如何：确定序列中的元素是否部分或全部满足条件 (LINQ to SQL)
更新：November 2007
如果序列中的所有元素都满足某一项条件，则 All<TSource> 运算符会返回 true。
如果序列中的任意一个元素满足某一项条件，则 Any 运算符会返回 true。
示例
下面的示例返回由至少下了一个订单的客户组成的序列。如果给定的 Customer 下了任何 Order，则 Where/where 子句的计算结果将为 true。
Dim OrdersQuery = _
From cust In db.Customers _
Where cust.Orders.Any() _
Select cust
var OrdersQuery =
from cust in db.Customers
where cust.Orders.Any()
select cust;
下面的 Visual Basic 代码确定未下订单的客户的列表，并确保对于该列表中的每一位客户，都提供了联系人名称。
Public Sub ContactsAvailable()
Dim db As New Northwnd("c:\northwnd.mdf")
Dim result = _
(From cust In db.Customers _
Where Not cust.Orders.Any() _
Select cust).All(AddressOf ContactAvailable)
If result Then
Console.WriteLine _
("All of the customers who have made no orders have a contact name")
Else
Console.WriteLine _
("Some customers who have made no orders have no contact name")
End If
End Sub
Function ContactAvailable(ByVal contact As Object) As Boolean
Dim cust As Customer = CType(contact, Customer)
Return (cust.ContactTitle Is Nothing OrElse _
cust.ContactTitle.Trim().Length = 0)
End Function
下面的 C# 示例返回由订单包含以“C”开头的 ShipCity 的客户组成的序列。返回结果中还包括未下订单的客户。（按照设计，对于空序列，All<TSource> 运算符返回 true。）通过使用 Count 运算符在控制台输出中消除了未下订单的客户。
var custEmpQuery =
from cust in db.Customers
where cust.Orders.All(o => o.ShipCity.StartsWith("C"))
orderby cust.CustomerID
select cust;
foreach (Customer custObj in custEmpQuery)
{
if (custObj.Orders.Count > 0)
Console.WriteLine("CustomerID: {0}", custObj.CustomerID);
foreach (Order ordObj in custObj.Orders)
{
Console.WriteLine("\t OrderID: {0}; ShipCity: {1}",
ordObj.OrderID, ordObj.ShipCity);
}
}