LINQ 查询示例

 

发布日期： 2017年1月

适用于： Dynamics 365 (online),Dynamics 365 (on-premises),Dynamics CRM 2016,Dynamics CRM Online

本主题包含许多 LINQ 查询示例。 有关完整示例，请参阅示例：复杂的 LINQ 查询。

本主题内容

简化 Where 子句

联接和简化 Where 子句

使用 Distinct 运算符

简单的内部联接

自联接

两个和多个联接

使用实体字段联接

后期绑定的左联接

使用等于运算符

使用不等于运算符

将基于方法的 LINQ 查询与 Where 子句结合使用

使用大于运算符

使用大于等于和小于等于运算符

使用包含运算符

使用不包含运算符

使用 StartsWith 和 EndsWith 运算符

使用 And 和 Or 运算符

使用 OrderBy 运算符

使用 First 和 Single 运算符

检索格式化值

使用 Skip 和 Take 运算符（不分页）

使用 FirstOrDefault 和 SingleOrDefault 运算符

对链接实体使用带条件的自联接

在 Where 子句中使用转换

使用分页排序

检索相关实体列（对于一对多关系）

使用 .Value 检索属性值

多个投影，转换为不同类型的新数据类型

使用 GetAttributeValue 方法

使用 Math 方法

使用多个 Select 和 Where 子句

使用 SelectMany

使用字符串操作

使用两个 Where 子句

使用 LoadProperty 检索相关记录

简化 Where 子句

以下示例演示如何检索其 Name 包含“Contoso”的客户列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_where1 = from a in svcContext.AccountSet
                    where a.Name.Contains("Contoso")
                    select a;
 foreach (var a in query_where1)
 {
  System.Console.WriteLine(a.Name + " " + a.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_where1 = From c In svcContext.AccountSet _
                    Where c.Name.Contains("Contoso") _
                    Select c

 For Each c In query_where1
  Console.WriteLine(c.Name & " " & c.Address1_City)
 Next c
End Using

以下示例演示如何检索其 Name 包含“Contoso”且 Address1_City为“Redmond”的客户的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_where2 = from a in svcContext.AccountSet
                    where a.Name.Contains("Contoso")
                    where a.Address1_City == "Redmond"
                    select a;

 foreach (var a in query_where2)
 {
  System.Console.WriteLine(a.Name + " " + a.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_where2 = From c In svcContext.AccountSet _
                    Where c.Name.Contains("Contoso") _
                    Where c.Address1_City.Equals("Redmond") _
                    Select c

 For Each c In query_where2
  Console.WriteLine(c.Name & " " & c.Address1_City)
 Next c
End Using

联接和简化 Where 子句

以下示例演示如何检索其客户 Name 包含“Contoso”、联系人 LastName 包含“Smith”且联系人是客户的主要联系人的客户 Name 和联系人 LastName。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_where3 = from c in svcContext.ContactSet
                    join a in svcContext.AccountSet
                    on c.ContactId equals a.PrimaryContactId.Id
                    where a.Name.Contains("Contoso")
                    where c.LastName.Contains("Smith")
                    select new
                    {
                     account_name = a.Name,
                     contact_name = c.LastName
                    };

 foreach (var c in query_where3)
 {
  System.Console.WriteLine("acct: " +
   c.account_name +
   "\t\t\t" +
   "contact: " +
   c.contact_name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_where3 = From c In svcContext.ContactSet _
                    Join a In svcContext.AccountSet _
                    On c.ContactId Equals a.account_primary_contact.Id _
                    Where a.Name.Contains("Contoso") _
                    Where c.LastName.Contains("Smith") _
                    Select New With {Key .account_name = a.Name,
                                     Key .contact_name = c.LastName}

 For Each c In query_where3
  Console.WriteLine("acct: " & c.account_name & vbTab & vbTab _
                    & vbTab & "contact: " & c.contact_name)
 Next c
End Using

使用 Distinct 运算符

以下示例演示如何检索联系人姓氏的明确列表。 虽然可能存在重复项，但每个姓名仅列出一次。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_distinct = (from c in svcContext.ContactSet
                       select c.LastName).Distinct();
 foreach (var c in query_distinct)
 {
  System.Console.WriteLine(c);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_distinct = ( _
     From c In svcContext.ContactSet _
     Select c.LastName).Distinct()
 For Each c In query_distinct
  Console.WriteLine(c)
 Next c
End Using

简单的内部联接

以下示例演示如何检索有关作为客户的主要联系人列出的客户和联系人的信息。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_join1 = from c in svcContext.ContactSet
                   join a in svcContext.AccountSet
                  on c.ContactId equals a.PrimaryContactId.Id
                   select new
                   {
                    c.FullName,
                    c.Address1_City,
                    a.Name,
                    a.Address1_Name
                   };
 foreach (var c in query_join1)
 {
  System.Console.WriteLine("acct: " +
   c.Name +
   "\t\t\t" +
   "contact: " +
   c.FullName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_join1 = From c In svcContext.ContactSet _
                   Join a In svcContext.AccountSet _
                   On c.ContactId Equals a.account_primary_contact.Id _
                   Select New With {Key c.FullName, Key c.Address1_City,
                                    Key a.Name, Key a.Address1_Name}
 For Each c In query_join1
  Console.WriteLine("acct: " & c.Name & vbTab & vbTab _
                    & vbTab & "contact: " & c.FullName)
 Next c
End Using

自联接

以下示例演示如何检索有关其中一个客户是另一个客户的上级单位的客户信息。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_join5 = from a in svcContext.AccountSet
                   join a2 in svcContext.AccountSet
                   on a.ParentAccountId.Id equals a2.AccountId

                   select new
                   {
                    account_name = a.Name,
                    account_city = a.Address1_City
                   };
 foreach (var c in query_join5)
 {
  System.Console.WriteLine(c.account_name + "  " + c.account_city);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_join5 = From a In svcContext.AccountSet _
                   Join a2 In svcContext.AccountSet _
                   On a.ParentAccountId.Id Equals a2.AccountId _
                   Select New With {
                         Key .account_name = a.Name,
                         Key .account_city = a.Address1_City
                         }
 For Each c In query_join5
  Console.WriteLine(c.account_name & "  " & c.account_city)
 Next c
End Using

两个和多个联接

以下示例演示如何检索其中联系人是客户的主要联系人且潜在顾客是客户的原始潜在顾客的客户、联系人和潜在顾客的信息。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_join4 = from a in svcContext.AccountSet
                   join c in svcContext.ContactSet
                   on a.PrimaryContactId.Id equals c.ContactId
                   join l in svcContext.LeadSet
                   on a.OriginatingLeadId.Id equals l.LeadId
                   select new
                   {
                    contact_name = c.FullName,
                    account_name = a.Name,
                    lead_name = l.FullName
                   };
 foreach (var c in query_join4)
 {
  System.Console.WriteLine(c.contact_name +
   "  " +
   c.account_name +
   "  " +
   c.lead_name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_join4 = From a In svcContext.AccountSet _
                   Join c In svcContext.ContactSet _
                   On a.PrimaryContactId.Id Equals c.ContactId _
                   Join l In svcContext.LeadSet _
                   On a.OriginatingLeadId.Id Equals l.LeadId _
                   Select New With {Key .contact_name = c.FullName,
                                    Key .account_name = a.Name,
                                    Key .lead_name = l.FullName}
 For Each c In query_join4
  Console.WriteLine(c.contact_name & "  " & c.account_name _
                    & "  " & c.lead_name)
 Next c
End Using

以下示例演示如何检索其中一个客户是另一个客户的上级单位且联系人是客户的主要联系人的客户和联系人信息。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_join6 = from c in svcContext.ContactSet
                   join a in svcContext.AccountSet
                   on c.ContactId equals a.PrimaryContactId.Id
                   join a2 in svcContext.AccountSet
                   on a.ParentAccountId.Id equals a2.AccountId
                   select new
                   {
                    contact_name = c.FullName,
                    account_name = a.Name
                   };
 foreach (var c in query_join6)
 {
  System.Console.WriteLine(c.contact_name + "  " + c.account_name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_join6 = From c In svcContext.ContactSet _
                   Join a In svcContext.AccountSet _
                   On c.ContactId Equals a.PrimaryContactId.Id _
                   Join a2 In svcContext.AccountSet _
                   On a.ParentAccountId.Id Equals a2.AccountId _
                   Select New With {Key .contact_name = c.FullName,
                                    Key .account_name = a.Name}
 For Each c In query_join6
  Console.WriteLine(c.contact_name & "  " & c.account_name)
 Next c
End Using

使用实体字段联接

以下示例演示如何从列表检索有关客户的信息

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var list_join = (from a in svcContext.AccountSet
                  join c in svcContext.ContactSet
                  on a.PrimaryContactId.Id equals c.ContactId
                  where a.Name == "Contoso Ltd" &&
                  a.Address1_Name == "Contoso Pharmaceuticals"
                  select a).ToList();
 foreach (var c in list_join)
 {
  System.Console.WriteLine("Account " + list_join[0].Name
      + " and it's primary contact "
      + list_join[0].PrimaryContactId.Id);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim list_join = ( _
     From a In svcContext.AccountSet _
     Join c In svcContext.ContactSet _
     On a.PrimaryContactId.Id Equals c.ContactId _
     Where a.Name.Equals("Contoso Ltd") _
     And a.Address1_Name.Equals("Contoso Pharmaceuticals") _
     Select a).ToList()
 For Each c In list_join
  Console.WriteLine("Account " & list_join(0).Name _
                    & " and it's primary contact " _
                    & list_join(0).PrimaryContactId.Id.ToString())
 Next c
End Using

后期绑定的左联接

以下示例显示左联接。 左联接设计用于从两个源中返回具有和不具有子级的父级。 父与子之间存在关联，但实际上可能不存在任何子级。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_join8 = from a in svcContext.AccountSet
                   join c in svcContext.ContactSet
                   on a.PrimaryContactId.Id equals c.ContactId
                   into gr
                   from c_joined in gr.DefaultIfEmpty()
                   select new
                   {
                    contact_name = c_joined.FullName,
                    account_name = a.Name
                   };
 foreach (var c in query_join8)
 {
  System.Console.WriteLine(c.contact_name + "  " + c.account_name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_join8 = From a In svcContext.AccountSet _
                   Group Join c In svcContext.ContactSet _
                   On a.PrimaryContactId.Id Equals c.ContactId Into gr = _
                   Group From c_joined In gr.DefaultIfEmpty() _
                   Select New With {Key .contact_name = c_joined.FullName,
                                    Key .account_name = a.Name}
 For Each c In query_join8
  Console.WriteLine(c.contact_name & "  " & c.account_name)
 Next c
End Using

使用等于运算符

以下示例演示如何检索其 FirstName 为“Colin”的联系人的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_equals1 = from c in svcContext.ContactSet
                     where c.FirstName.Equals("Colin")
                     select new
                     {
                      c.FirstName,
                      c.LastName,
                      c.Address1_City
                     };
 foreach (var c in query_equals1)
 {
  System.Console.WriteLine(c.FirstName +
   " " + c.LastName +
   " " + c.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_equals1 = From c In svcContext.ContactSet _
                     Where c.FirstName.Equals("Colin") _
                     Select New With {Key c.FirstName,
                                      Key c.LastName,
                                      Key c.Address1_City}
 For Each c In query_equals1
  Console.WriteLine(c.FirstName & " " & c.LastName & " " _
                    & c.Address1_City)
 Next c
End Using

以下示例演示如何检索其 FamilyStatusCode 为 3 的联系人的列表。 这对应于“婚姻状况”的选项“离异”。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_equals2 = from c in svcContext.ContactSet
                     where c.FamilyStatusCode.Equals(3)
                     select new
                     {
                      c.FirstName,
                      c.LastName,
                      c.Address1_City
                     };
 foreach (var c in query_equals2)
 {
  System.Console.WriteLine(c.FirstName +
   " " + c.LastName +
   " " + c.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_equals2 = From c In svcContext.ContactSet _
                     Where c.FamilyStatusCode.Equals(3) _
                     Select New With {Key c.FirstName,
                                      Key c.LastName,
                                      Key c.Address1_City}
 For Each c In query_equals2
  Console.WriteLine(c.FirstName & " " & c.LastName & " " _
                    & c.Address1_City)
 Next c
End Using

使用不等于运算符

以下示例演示如何检索其 Address1_City 不为“Redmond”的联系人的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_ne1 = from c in svcContext.ContactSet
                 where c.Address1_City != "Redmond"
                 select new
                 {
                  c.FirstName,
                  c.LastName,
                  c.Address1_City
                 };
 foreach (var c in query_ne1)
 {
  System.Console.WriteLine(c.FirstName + " " +
   c.LastName + " " + c.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_ne1 = From c In svcContext.ContactSet _
                 Where c.Address1_City IsNot "Redmond" _
                 Select New With {Key c.FirstName,
                                  Key c.LastName,
                                  Key c.Address1_City}
 For Each c In query_ne1
  Console.WriteLine(c.FirstName & " " & c.LastName _
                    & " " & c.Address1_City)
 Next c
End Using

以下示例演示如何检索其 FirstName 不为“Colin”的联系人的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_ne2 = from c in svcContext.ContactSet
                 where !c.FirstName.Equals("Colin")
                 select new
                 {
                  c.FirstName,
                  c.LastName,
                  c.Address1_City
                 };

 foreach (var c in query_ne2)
 {
  System.Console.WriteLine(c.FirstName + " " +
   c.LastName + " " + c.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_ne2 = From c In svcContext.ContactSet _
                 Where (Not c.FirstName.Equals("Colin")) _
                 Select New With {Key c.FirstName,
                                  Key c.LastName,
                                  Key c.Address1_City}

 For Each c In query_ne2
  Console.WriteLine(c.FirstName & " " & c.LastName & " " _
                    & c.Address1_City)
 Next c
End Using

将基于方法的 LINQ 查询与 Where 子句结合使用

以下示例演示如何检索其 LastName 为“Smith”或包含“Smi”的联系人的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var methodResults = svcContext.ContactSet
  .Where(a => a.LastName == "Smith");
 var methodResults2 = svcContext.ContactSet
  .Where(a => a.LastName.StartsWith("Smi"));
 Console.WriteLine();
 Console.WriteLine("Method query using Lambda expression");
 Console.WriteLine("---------------------------------------");
 foreach (var a in methodResults)
 {
  Console.WriteLine("Name: " + a.FirstName + " " + a.LastName);
 }
 Console.WriteLine("---------------------------------------");
 Console.WriteLine("Method query 2 using Lambda expression");
 Console.WriteLine("---------------------------------------");
 foreach (var a in methodResults2)
 {
  Console.WriteLine("Name: " + a.Attributes["firstname"] +
   " " + a.Attributes["lastname"]);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim methodResults = svcContext.ContactSet _
                     .Where(Function(a) a.LastName.Equals("Smith"))
 Dim methodResults2 = svcContext.ContactSet _
                      .Where(Function(a) a.LastName.StartsWith("Smi"))
 Console.WriteLine()
 Console.WriteLine("Method query using Lambda expression")
 Console.WriteLine("---------------------------------------")
 For Each a In methodResults
  Console.WriteLine("Name: " & a.FirstName & " " & a.LastName)
 Next a
 Console.WriteLine("---------------------------------------")
 Console.WriteLine("Method query 2 using Lambda expression")
 Console.WriteLine("---------------------------------------")
 For Each a In methodResults2
  Console.WriteLine("Name: " & a.Attributes("firstname").ToString() _
                    & " " & a.Attributes("lastname").ToString())
 Next a
End Using

使用大于运算符

以下示例演示如何检索 Anniversary 日期晚于 2010 年 2 月 5 日的联系人列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_gt1 = from c in svcContext.ContactSet
                 where c.Anniversary > new DateTime(2010, 2, 5)
                 select new
                 {
                  c.FirstName,
                  c.LastName,
                  c.Address1_City
                 };

 foreach (var c in query_gt1)
 {
  System.Console.WriteLine(c.FirstName + " " +
   c.LastName + " " + c.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_gt1 = From c In svcContext.ContactSet _
                 Where c.Anniversary > New Date(2010, 2, 5) _
                 Select New With {Key c.FirstName,
                                  Key c.LastName,
                                  Key c.Address1_City}

 For Each c In query_gt1
  Console.WriteLine(c.FirstName & " " & c.LastName _
                    & " " & c.Address1_City)
 Next c
End Using

以下示例显示如何检索 CreditLimit 大于 $20,000 的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_gt2 = from c in svcContext.ContactSet
                 where c.CreditLimit.Value > 20000
                 select new
                 {
                  c.FirstName,
                  c.LastName,
                  c.Address1_City
                 };
 foreach (var c in query_gt2)
 {
  System.Console.WriteLine(c.FirstName + " " +
   c.LastName + " " + c.Address1_City);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_gt2 = From c In svcContext.ContactSet _
                 Where c.CreditLimit.Value > 20000 _
                 Select New With {Key c.FirstName,
                                  Key c.LastName,
                                  Key c.Address1_City}
 For Each c In query_gt2
  Console.WriteLine(c.FirstName & " " & c.LastName _
                    & " " & c.Address1_City)
 Next c
End Using

使用大于等于和小于等于运算符

以下示例显示如何检索 CreditLimit 大于 $200、小于 $400 的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_gele1 = from c in svcContext.ContactSet
                   where c.CreditLimit.Value >= 200 &&
                   c.CreditLimit.Value <= 400
                   select new
                   {
                    c.FirstName,
                    c.LastName
                   };
 foreach (var c in query_gele1)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_gele1 = From c In svcContext.ContactSet _
                   Where c.CreditLimit.Value >= 200 _
                   AndAlso c.CreditLimit.Value <= 400 _
                   Select New With {Key c.FirstName,
                                    Key c.LastName}
 For Each c In query_gele1
  Console.WriteLine(c.FirstName &amp; " " &amp; c.LastName)
 Next c
End Using

使用包含运算符

以下示例演示如何检索其 Description 包含“Alpine”的联系人的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_contains1 = from c in svcContext.ContactSet
                       where c.Description.Contains("Alpine")
                       select new
                       {
                        c.FirstName,
                        c.LastName
                       };
 foreach (var c in query_contains1)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_contains1 = From c In svcContext.ContactSet _
                       Where c.Description.Contains("Alpine") _
                       Select New With {Key c.FirstName,
                                        Key c.LastName}
 For Each c In query_contains1
  Console.WriteLine(c.FirstName & " " & c.LastName)
 Next c
End Using

使用不包含运算符

以下示例演示如何检索其 Description 不包含“Coho”的联系人的列表。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_contains2 = from c in svcContext.ContactSet
                       where !c.Description.Contains("Coho")
                       select new
                       {
                        c.FirstName,
                        c.LastName
                       };
 foreach (var c in query_contains2)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_contains2 = From c In svcContext.ContactSet _
                       Where (Not c.Description.Contains("Coho")) _
                       Select New With {Key c.FirstName,
                                        Key c.LastName}
 For Each c In query_contains2
  Console.WriteLine(c.FirstName.ToString() & " " _
                    & c.LastName.ToString())
 Next c
End Using

使用 StartsWith 和 EndsWith 运算符

以下示例显示如何检索 FirstName 以“Bri”开头的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_startswith1 = from c in svcContext.ContactSet
                         where c.FirstName.StartsWith("Bri")
                         select new
                         {
                          c.FirstName,
                          c.LastName
                         };
 foreach (var c in query_startswith1)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_startswith1 = From c In svcContext.ContactSet _
                         Where c.FirstName.StartsWith("Bri") _
                         Select New With {Key c.FirstName,
                                          Key c.LastName}
 For Each c In query_startswith1
  Console.WriteLine(c.FirstName.ToString() & " " _
                    & c.LastName.ToString())
 Next c
End Using

以下示例演示如何检索 LastName 以“cox”结束的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_endswith1 = from c in svcContext.ContactSet
                       where c.LastName.EndsWith("cox")
                       select new
                       {
                        c.FirstName,
                        c.LastName
                       };
 foreach (var c in query_endswith1)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_endswith1 = From c In svcContext.ContactSet _
                       Where c.LastName.EndsWith("cox") _
                       Select New With {Key c.FirstName,
                                        Key c.LastName}
 For Each c In query_endswith1
  Console.WriteLine(c.FirstName.ToString() & " " _
                    & c.LastName.ToString())
 Next c
End Using

使用 And 和 Or 运算符

以下示例演示如何检索其 Address1_City 为“Redmond”或“Bellevue”且 CreditLimit 大于 $200 的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_andor1 = from c in svcContext.ContactSet
                    where ((c.Address1_City == "Redmond" ||
                    c.Address1_City == "Bellevue") &&
                    (c.CreditLimit.Value != null &&
                    c.CreditLimit.Value >= 200))
                    select c;

 foreach (var c in query_andor1)
 {
  System.Console.WriteLine(c.LastName + ", " + c.FirstName + " " +
   c.Address1_City + " " + c.CreditLimit.Value);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_andor1 = From c In svcContext.ContactSet _
                    Where c.Address1_City.Equals("Redmond") _
                    OrElse c.Address1_City.Equals("Bellevue") _
                    AndAlso c.CreditLimit.Value >= 200 _
                    Select New With {Key c.FirstName,
                                     Key c.LastName,
                                     Key c.CreditLimit,
                                     Key c.Address1_City}
 For Each c In query_andor1
  Console.WriteLine(c.LastName.ToString() & ", " _
                    & c.FirstName.ToString() & " " _
                    & c.Address1_City.ToString() & " " _
                    & c.CreditLimit.Value.ToString())
 Next c
End Using

使用 OrderBy 运算符

以下示例演示如何检索按 CreditLimit 降序排序的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_orderby1 = from c in svcContext.ContactSet
                      where !c.CreditLimit.Equals(null)
                      orderby c.CreditLimit descending
                      select new
                      {
                       limit = c.CreditLimit,
                       first = c.FirstName,
                       last = c.LastName
                      };
 foreach (var c in query_orderby1)
 {
  System.Console.WriteLine(c.limit.Value + " " +
   c.last + ", " + c.first);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_orderby1 = From c In svcContext.ContactSet _
                      Where (Not c.CreditLimit.Equals(Nothing)) _
                      Order By c.CreditLimit Descending _
                      Select New With {Key .limit = c.CreditLimit,
                                       Key .first = c.FirstName,
                                       Key .last = c.LastName}
 For Each c In query_orderby1
  Console.WriteLine(c.limit.Value & " " & c.last & ", " _
                    & c.first)
 Next c
End Using

以下示例演示如何检索按 LastName 降序和 FirstName 升序排序的联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_orderby2 = from c in svcContext.ContactSet
                      orderby c.LastName descending,
                      c.FirstName ascending
                      select new
                      {
                       first = c.FirstName,
                       last = c.LastName
                      };

 foreach (var c in query_orderby2)
 {
  System.Console.WriteLine(c.last + ", " + c.first);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_orderby2 = From c In svcContext.ContactSet _
                      Order By c.LastName Descending, _
                      c.FirstName Ascending _
                      Select New With {Key .first = c.FirstName,
                                       Key .last = c.LastName}

 For Each c In query_orderby2
  Console.WriteLine(c.last & ", " & c.first)
 Next c
End Using

使用 First 和 Single 运算符

以下示例演示如何仅检索返回的第一条联系人记录以及仅检索与条件匹配的一条联系人记录。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 Contact firstcontact = svcContext.ContactSet.First();

 Contact singlecontact = svcContext.ContactSet.Single(c => c.ContactId == _contactId1);
 System.Console.WriteLine(firstcontact.LastName + ", " +
  firstcontact.FirstName + " is the first contact");
 System.Console.WriteLine("==========================");
 System.Console.WriteLine(singlecontact.LastName + ", " +
  singlecontact.FirstName + " is the single contact");
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim firstcontact As Contact = svcContext.ContactSet _
                               .First()
 Console.WriteLine(firstcontact.LastName & ", " _
                   & firstcontact.FirstName _
                   & " is the first contact")
 Console.WriteLine("==========================")
 Dim singlecontact As Contact =
     svcContext.ContactSet _
     .Single(Function(c) c.ContactId.Value.Equals(_contactId1))
 Console.WriteLine(singlecontact.LastName & ", " _
                   & singlecontact.FirstName _
                   & " is the single contact")
End Using

检索格式化值

以下示例演示如何检索选项集选项的标签，在本例中为当前记录状态的值。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var list_retrieve1 = from c in svcContext.ContactSet
                      where c.ContactId == _contactId1
                      select new { StatusReason = c.FormattedValues["statuscode"] };
 foreach (var c in list_retrieve1)
 {
  System.Console.WriteLine("Status: " + c.StatusReason);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim list_retrieve1 = From c In svcContext.ContactSet _
                      Where c.ContactId.Value.Equals(_contactId1) _
                      Select New With
                             {Key .StatusReason =
                                 c.FormattedValues("statuscode")}
 For Each c In list_retrieve1
  Console.WriteLine("Status: " & c.StatusReason)
 Next c
End Using

使用 Skip 和 Take 运算符（不分页）

以下示例演示如何使用 Skip 和 Take 运算符在跳过其 LastName 不为“Parker”的两条记录后仅检索两条记录。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{

 var query_skip = (from c in svcContext.ContactSet
                   where c.LastName != "Parker"
                   orderby c.FirstName
                   select new
                       {
                        last = c.LastName,
                        first = c.FirstName
                       }).Skip(2).Take(2);
 foreach (var c in query_skip)
 {
  System.Console.WriteLine(c.first + " " + c.last);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_skip = ( _
     From c In svcContext.ContactSet _
     Where c.LastName IsNot "Parker" _
     Order By c.FirstName _
     Select New With {Key .last = c.LastName,
                      Key .first = c.FirstName}).Skip(2).Take(2)
 For Each c In query_skip
  Console.WriteLine(c.first & " " & c.last)
 Next c
End Using

使用 FirstOrDefault 和 SingleOrDefault 运算符

FirstOrDefault 运算符返回序列中的第一个元素，如果未找到任何元素，则返回默认值。SingleOrDefault 运算符返回序列中单个特定的元素，如果未找到此元素，则返回该元素的默认值。 以下示例演示如何使用这些运算符。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{

 Contact firstorcontact = svcContext.ContactSet.FirstOrDefault();

 Contact singleorcontact = svcContext.ContactSet
  .SingleOrDefault(c => c.ContactId == _contactId1);


 System.Console.WriteLine(firstorcontact.FullName +
  " is the first contact");
 System.Console.WriteLine("==========================");
 System.Console.WriteLine(singleorcontact.FullName +
  " is the single contact");
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim firstorcontact As Contact =
     svcContext.ContactSet.FirstOrDefault()
 Console.WriteLine(firstorcontact.FullName & " is the first contact")

 Console.WriteLine("==========================")
 Dim singleorcontact As Contact =
     svcContext.ContactSet _
     .SingleOrDefault(Function(c) c.ContactId.Value.Equals(_contactId1))
 Console.WriteLine(singleorcontact.FullName & " is the single contact")
End Using

对链接实体使用带条件的自联接

以下示例演示如何检索其中一个客户是另一个客户的上级单位的两个客户名称。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_joincond = from a1 in svcContext.AccountSet
                      join a2 in svcContext.AccountSet
                      on a1.ParentAccountId.Id equals a2.AccountId
                      where a2.AccountId == _accountId1
                      select new { Account = a1, Parent = a2 };
 foreach (var a in query_joincond)
 {
  System.Console.WriteLine(a.Account.Name + " " + a.Parent.Name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_joincond = From a1 In svcContext.AccountSet _
                      Join a2 In svcContext.AccountSet _
                      On a1.ParentAccountId.Id Equals a2.AccountId _
                      Where a2.AccountId.Value.Equals(_accountId1) _
                      Select New With {Key .Account = a1,
                                       Key .Parent = a2}
 For Each a In query_joincond
  Console.WriteLine(a.Account.Name & " " & a.Parent.Name)
 Next a
End Using

在 Where 子句中使用转换

以下示例演示如何检索其周年纪念日晚于 2010 年 1 月 1 日的特定联系人。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_wheretrans = from c in svcContext.ContactSet
                        where c.ContactId == _contactId1 &&
                        c.Anniversary > DateTime.Parse("1/1/2010")
                        select new
                        {
                         c.FirstName,
                         c.LastName
                        };
 foreach (var c in query_wheretrans)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_wheretrans = From c In svcContext.ContactSet _
                        Where c.ContactId.Value.Equals(_contactId1) _
                        AndAlso c.Anniversary > Date.Parse("1/1/2010") _
                        Select New With {Key c.FirstName,
                                         Key c.LastName}
 For Each c In query_wheretrans
  Console.WriteLine(c.FirstName & " " & c.LastName)
 Next c
End Using

使用分页排序

以下示例显示多层柱排序和一个额外条件。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_pagingsort1 = (from c in svcContext.ContactSet
                          where c.LastName != "Parker"
                          orderby c.LastName ascending,
                          c.FirstName descending
                          select new { c.FirstName, c.LastName })
                          .Skip(2).Take(2);
 foreach (var c in query_pagingsort1)
 {
  System.Console.WriteLine(c.FirstName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_pagingsort1 = ( _
     From c In svcContext.ContactSet _
     Where c.LastName IsNot "Parker" _
     Order By c.LastName Ascending, c.FirstName Descending _
     Select New With {Key c.FirstName,
                      Key c.LastName}).Skip(2).Take(2)
 For Each c In query_pagingsort1
  Console.WriteLine(c.FirstName & " " & c.LastName)
 Next c
End Using

以下示例演示其中要排序的列不同于要检索的列的分页排序。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_pagingsort2 = (from c in svcContext.ContactSet
                          where c.LastName != "Parker"
                          orderby c.FirstName descending
                          select new { c.FirstName }).Skip(2).Take(2);
 foreach (var c in query_pagingsort2)
 {
  System.Console.WriteLine(c.FirstName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_pagingsort2 = ( _
     From c In svcContext.ContactSet _
     Where c.LastName IsNot "Parker" _
     Order By c.FirstName Descending _
     Select New With {Key c.FirstName}).Skip(2).Take(2)
 For Each c In query_pagingsort2
  Console.WriteLine(c.FirstName)
 Next c
End Using

以下示例演示如何检索前 10 条记录。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_pagingsort3 = (from c in svcContext.ContactSet
                          where c.LastName.StartsWith("W")
                          orderby c.MiddleName ascending,
                          c.FirstName descending
                          select new
                          {
                           c.FirstName,
                           c.MiddleName,
                           c.LastName
                          }).Take(10);
 foreach (var c in query_pagingsort3)
 {
  System.Console.WriteLine(c.FirstName + " " +
   c.MiddleName + " " + c.LastName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_pagingsort3 = ( _
     From c In svcContext.ContactSet _
     Where c.LastName.StartsWith("W") _
     Order By c.MiddleName Ascending, c.FirstName Descending _
     Select New With {Key c.FirstName,
                      Key c.MiddleName,
                      Key c.LastName}).Take(10)
 For Each c In query_pagingsort3
  Console.WriteLine(c.FirstName & " " & c.MiddleName & " " & c.LastName)
 Next c
End Using

检索相关实体列（对于一对多关系）

以下示例演示如何从相关客户和联系人记录检索列。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_retrieve1 = from c in svcContext.ContactSet
                       join a in svcContext.AccountSet
                       on c.ContactId equals a.PrimaryContactId.Id
                       where c.ContactId != _contactId1
                       select new { Contact = c, Account = a };
 foreach (var c in query_retrieve1)
 {
  System.Console.WriteLine("Acct: " + c.Account.Name +
   "\t\t" + "Contact: " + c.Contact.FullName);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_retrieve1 = From c In svcContext.ContactSet _
                       Join a In svcContext.AccountSet _
                       On c.ContactId Equals a.PrimaryContactId.Id _
                       Where Not c.ContactId.Value.Equals(_contactId1) _
                       Select New With {Key .Contact = c,
                                        Key .Account = a}
 For Each c In query_retrieve1
  Console.WriteLine("Acct: " & c.Account.Name & vbTab & vbTab _
                    & "Contact: " & c.Contact.FullName)
 Next c
End Using

使用 .Value 检索属性值

以下示例显示如何使用 Value 访问属性的值。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{

 var query_value = from c in svcContext.ContactSet
                   where c.ContactId != _contactId2
                   select new
                   {
                    ContactId = c.ContactId != null ?
                     c.ContactId.Value : Guid.Empty,
                    NumberOfChildren = c.NumberOfChildren != null ?
                     c.NumberOfChildren.Value : default(int),
                    CreditOnHold = c.CreditOnHold != null ?
                     c.CreditOnHold.Value : default(bool),
                    Anniversary = c.Anniversary != null ?
                     c.Anniversary.Value : default(DateTime)
                   };

 foreach (var c in query_value)
 {
  System.Console.WriteLine(c.ContactId + " " + c.NumberOfChildren + 
   " " + c.CreditOnHold + " " + c.Anniversary);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_value = From c In svcContext.ContactSet _
                   Where Not c.ContactId.Value.Equals(_contactId2) _
                   Select New With
                          {Key .ContactId = If(
                                  c.ContactId IsNot Nothing,
                                  c.ContactId.Value,
                                  Guid.Empty),
                           Key .NumberOfChildren = If(
                               c.NumberOfChildren IsNot Nothing,
                               c.NumberOfChildren.Value, Nothing),
                           Key .CreditOnHold = If(
                               c.CreditOnHold IsNot Nothing,
                               c.CreditOnHold.Value,
                               Nothing),
                           Key .Anniversary = If(
                               c.Anniversary IsNot Nothing,
                               c.Anniversary.Value,
                               Nothing)}

 For Each c In query_value
  Console.WriteLine(c.ContactId.ToString() & " " _
                    & c.NumberOfChildren & " " _
                    & c.CreditOnHold & " " & c.Anniversary)
 Next c
End Using

多个投影，转换为不同类型的新数据类型

以下示例演示多个投影以及如何将值转换为不同类型。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_projections = from c in svcContext.ContactSet
                         where c.ContactId == _contactId1
                         && c.NumberOfChildren != null && 
                         c.Anniversary.Value != null
                         select new
                         {
                          Contact = new Contact { 
                           LastName = c.LastName, 
                           NumberOfChildren = c.NumberOfChildren 
                          },
                          NumberOfChildren = (double)c.NumberOfChildren,
                          Anniversary = c.Anniversary.Value.AddYears(1),
                         };
 foreach (var c in query_projections)
 {
  System.Console.WriteLine(c.Contact.LastName + " " + 
   c.NumberOfChildren + " " + c.Anniversary);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_projections = From c In svcContext.ContactSet _
                         Where c.ContactId.Value.Equals(_contactId1) _
                         And Not c.NumberOfChildren.Equals(Nothing) _
                         And Not c.Anniversary.Equals(Nothing) _
        Select New With
               {Key .Contact =
                   New Contact With
                   {.LastName = c.LastName,
                    .NumberOfChildren = c.NumberOfChildren},
                Key .NumberOfChildren = CDbl(c.NumberOfChildren),
                Key .Anniversary = c.Anniversary.Value.AddYears(1)}
 For Each c In query_projections
  Console.WriteLine(c.Contact.LastName & " " & c.NumberOfChildren _
                    & " " & c.Anniversary)
 Next c
End Using

使用 GetAttributeValue 方法

以下示例演示如何使用 GetAttributeValue<T> 方法。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_getattrib = from c in svcContext.ContactSet
                       where c.GetAttributeValue<Guid>("contactid") != _contactId1
                       select new
                       {
                        ContactId = c.GetAttributeValue<Guid?>("contactid"),
                        NumberOfChildren = c.GetAttributeValue<int?>("numberofchildren"),
                        CreditOnHold = c.GetAttributeValue<bool?>("creditonhold"),
                        Anniversary = c.GetAttributeValue<DateTime?>("anniversary"),
                       };

 foreach (var c in query_getattrib)
 {
  System.Console.WriteLine(c.ContactId + " " + c.NumberOfChildren + 
   " " + c.CreditOnHold + " " + c.Anniversary);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_getattrib = From c In svcContext.ContactSet _
                       Where Not c.GetAttributeValue(Of Guid)("contactid").Equals( _
                        _contactId1) _
                       Select New With
                              {Key .ContactId =
                                  c.GetAttributeValue(Of Guid?)("contactid"),
                               Key .NumberOfChildren =
                               c.GetAttributeValue(Of Integer?)("numberofchildren"),
                               Key .CreditOnHold =
                               c.GetAttributeValue(Of Boolean?)("creditonhold"),
                               Key .Anniversary =
                               c.GetAttributeValue(Of Date?)("anniversary")}

 For Each c In query_getattrib
  Console.WriteLine(c.ContactId.ToString() & " " _
                    & c.NumberOfChildren & " " & c.CreditOnHold _
                    & " " & c.Anniversary)
 Next c
End Using

使用 Math 方法

以下示例演示如何使用各种 Math 方法。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_math = from c in svcContext.ContactSet
                  where c.ContactId != _contactId2
                  && c.Address1_Latitude != null && 
                  c.Address1_Longitude != null
                  select new
                  {
                   Round = Math.Round(c.Address1_Latitude.Value),
                   Floor = Math.Floor(c.Address1_Latitude.Value),
                   Ceiling = Math.Ceiling(c.Address1_Latitude.Value),
                   Abs = Math.Abs(c.Address1_Latitude.Value),
                  };
 foreach (var c in query_math)
 {
  System.Console.WriteLine(c.Round + " " + c.Floor + 
   " " + c.Ceiling + " " + c.Abs);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_math = From c In svcContext.ContactSet _
                  Where Not c.ContactId.Value.Equals(_contactId2) _
                  AndAlso c.Address1_Latitude IsNot Nothing _
                  AndAlso c.Address1_Longitude IsNot Nothing _
                  Select New With
                         {Key .Round =
                             Math.Round(c.Address1_Latitude.Value),
                          Key .Floor =
                             Math.Floor(c.Address1_Latitude.Value),
                          Key .Ceiling =
                             Math.Ceiling(c.Address1_Latitude.Value),
                          Key .Abs =
                             Math.Abs(c.Address1_Latitude.Value)}
 For Each c In query_math
  Console.WriteLine(c.Round & " " & c.Floor & " " _
                    & c.Ceiling & " " & c.Abs)
 Next c
End Using

使用多个 Select 和 Where 子句

以下示例显示使用基于方法的查询语法的多个 Select 和 Where 子句。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_multiselect = svcContext.IncidentSet
                        .Where(i => i.IncidentId != _incidentId1)
                        .Select(i => i.incident_customer_accounts)
                        .Where(a => a.AccountId != _accountId2)
                        .Select(a => a.account_primary_contact)
                        .OrderBy(c => c.FirstName)
                        .Select(c => c.ContactId);
 foreach (var c in query_multiselect)
 {
  System.Console.WriteLine(c.GetValueOrDefault());
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_multiselect =
     svcContext.IncidentSet _
     .Where(Function(i) Not i.IncidentId.Value.Equals(_incidentId1)) _
     .Select(Function(i) i.incident_customer_accounts) _
     .Where(Function(a) Not a.AccountId.Value.Equals(_accountId2)) _
     .Select(Function(a) a.account_primary_contact) _
     .OrderBy(Function(c) c.FirstName).Select(Function(c) c.ContactId)
 For Each c In query_multiselect
  Console.WriteLine(c.GetValueOrDefault())
 Next c
End Using

使用 SelectMany

以下示例演示如何使用 SelectMany 方法。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_selectmany = svcContext.ContactSet
                        .Where(c => c.ContactId != _contactId2)
                        .SelectMany(c => c.account_primary_contact)
                        .OrderBy(a => a.Name);
 foreach (var c in query_selectmany)
 {
  System.Console.WriteLine(c.AccountId + " " + c.Name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_selectmany =
     svcContext.ContactSet _
     .Where(Function(c) Not c.ContactId.Value.Equals(_contactId2)) _
     .SelectMany(Function(c) c.account_primary_contact) _
     .OrderBy(Function(a) a.Name)
 For Each c In query_selectmany
  Console.WriteLine(c.AccountId.ToString() & " " & c.Name)
 Next c
End Using

使用字符串操作

以下示例演示如何使用各种 String 方法。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_string = from c in svcContext.ContactSet
                    where c.ContactId == _contactId2
                    select new
                    {
                     IndexOf = c.FirstName.IndexOf("contact"),
                     Insert = c.FirstName.Insert(1, "Insert"),
                     Remove = c.FirstName.Remove(1, 1),
                     Substring = c.FirstName.Substring(1, 1),
                     ToUpper = c.FirstName.ToUpper(),
                     ToLower = c.FirstName.ToLower(),
                     TrimStart = c.FirstName.TrimStart(),
                     TrimEnd = c.FirstName.TrimEnd(),
                    };

 foreach (var c in query_string)
 {
  System.Console.WriteLine(c.IndexOf + "\n" + c.Insert + "\n" + 
   c.Remove + "\n" + c.Substring + "\n"
                           + c.ToUpper + "\n" + c.ToLower + 
                           "\n" + c.TrimStart + " " + c.TrimEnd);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_string = From c In svcContext.ContactSet _
                    Where c.ContactId.Value.Equals(_contactId2) _
                    Select New With
                           {Key .IndexOf = c.FirstName.IndexOf("contact"),
                            Key .Insert = c.FirstName.Insert(1, "Insert"),
                            Key .Remove = c.FirstName.Remove(1, 1),
                            Key .Substring = c.FirstName.Substring(1, 1),
                            Key .ToUpper = c.FirstName.ToUpper(),
                            Key .ToLower = c.FirstName.ToLower(),
                            Key .TrimStart = c.FirstName.TrimStart(),
                            Key .TrimEnd = c.FirstName.TrimEnd()}

 For Each c In query_string
  Console.WriteLine(c.IndexOf & vbLf & c.Insert & vbLf _
                    & c.Remove & vbLf & c.Substring & vbLf _
                    & c.ToUpper & vbLf & c.ToLower & vbLf _
                    & c.TrimStart & " " & c.TrimEnd)
 Next c
End Using

使用两个 Where 子句

以下示例演示如何使用两个 Where 子句。

using (ServiceContext svcContext = new ServiceContext(_serviceProxy))
{
 var query_twowhere = from a in svcContext.AccountSet
                      join c in svcContext.ContactSet 
                      on a.PrimaryContactId.Id equals c.ContactId
                      where c.LastName == "Smith" && c.CreditOnHold != null
                      where a.Name == "Contoso Ltd"
                      orderby a.Name
                      select a;
 foreach (var c in query_twowhere)
 {
  System.Console.WriteLine(c.AccountId + " " + c.Name);
 }
}

Using svcContext As New ServiceContext(_serviceProxy)
 Dim query_twowhere = From a In svcContext.AccountSet _
                      Join c In svcContext.ContactSet _
                      On a.PrimaryContactId.Id Equals c.ContactId _
                      Where c.LastName.Equals("Smith") _
                      AndAlso c.CreditOnHold IsNot Nothing _
                      Where a.Name.Equals("Contoso Ltd") _
                      Order By a.Name _
                      Select a
 For Each c In query_twowhere
  Console.WriteLine(c.AccountId.ToString() & " " & c.Name)
 Next c
End Using

使用 LoadProperty 检索相关记录

以下示例演示如何使用 LoadProperty 访问相关记录。

Contact benAndrews = svcContext.ContactSet.Where(c => c.FullName == "Ben Andrews").FirstOrDefault();
if (benAndrews != null)
{
 //benAndrews.Contact_Tasks is null until LoadProperty is used.
 svcContext.LoadProperty(benAndrews, "Contact_Tasks");
 Task benAndrewsFirstTask = benAndrews.Contact_Tasks.FirstOrDefault();
 if (benAndrewsFirstTask != null)
 {
  Console.WriteLine("Ben Andrews first task with Subject: '{0}' retrieved.", benAndrewsFirstTask.Subject);
 }
}

另请参阅

使用 LINQ（.NET 语言集成查询）构建查询
示例：创建 LINQ 查询

Microsoft Dynamics 365

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