データをフィルター選択する方法 (Entity Framework)
このトピックでは、クエリ結果をフィルター選択する方法について説明します。 この例では、2,500 ドルを超えるすべてのオンライン注文を表す SalesOrderHeader オブジェクトのコレクションが返されます。 次の Entity Framework クエリ テクノロジを使用して同じことを行う例が紹介されています。
LINQ to Entities
Entity SQL と ObjectQuery<T>
ObjectQuery<T> のクエリ ビルダー メソッド
このトピックの例には、Adventure Works Sales Model が使用されています。このトピックのコードを実行するには、あらかじめプロジェクトに Adventure Works Sales Model を追加し、Entity Framework を使用するようにプロジェクトを構成しておく必要があります。詳細については、「Entity Data Model ウィザードを使用する方法 (Entity Framework)」、または「Entity Framework プロジェクトを手動で構成する方法」、および「Entity Data Model を手動で定義する方法 (Entity Framework)」を参照してください。
例
The following is the LINQ to Entities example.
Using context As New AdventureWorksEntities()
' Specify the order amount.
Dim orderCost As Integer = 2500
' Define a LINQ query that returns only online orders
' more than the specified amount.
Dim onlineOrders = From order In context.SalesOrderHeaders _
Where order.OnlineOrderFlag = True AndAlso order.TotalDue > orderCost _
Select order
' Print order information.
For Each onlineOrder In onlineOrders
Console.WriteLine("Order ID: {0} Order date: ", onlineOrder.SalesOrderID)
Console.WriteLine("Order date: {0:d}", onlineOrder.OrderDate)
Console.WriteLine("Order number: {0}", onlineOrder.SalesOrderNumber)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
// Specify the order amount.
int orderCost = 2500;
// Define a LINQ query that returns only online orders
// more than the specified amount.
var onlineOrders =
from order in context.SalesOrderHeaders
where order.OnlineOrderFlag == true &&
order.TotalDue > orderCost
select order;
// Print order information.
foreach (var onlineOrder in onlineOrders)
{
Console.WriteLine("Order ID: {0} Order date: "
+ "{1:d} Order number: {2}",
onlineOrder.SalesOrderID,
onlineOrder.OrderDate,
onlineOrder.SalesOrderNumber);
}
}
The following is the Entity SQL example.
Using context As New AdventureWorksEntities()
' Specify the order amount.
Dim orderCost As Decimal = 2500
' Specify the Entity SQL query that returns only online orders
' more than the specified amount.
Dim queryString As String = "SELECT VALUE o FROM AdventureWorksEntities.SalesOrderHeaders AS o " & _
" WHERE o.OnlineOrderFlag = TRUE AND o.TotalDue > @ordercost"
' Define an ObjectQuery and pass the maxOrderCost parameter.
Dim onlineOrders As New ObjectQuery(Of SalesOrderHeader)(queryString, context)
onlineOrders.Parameters.Add(New ObjectParameter("ordercost", orderCost))
' Print order information.
For Each onlineOrder In onlineOrders
Console.WriteLine("Order ID: {0} Order date: {1:d} Order number: {2}", _
onlineOrder.SalesOrderID, onlineOrder.OrderDate, onlineOrder.SalesOrderNumber)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
// Specify the order amount.
decimal orderCost = 2500;
// Specify the Entity SQL query that returns only online orders
// more than the specified amount.
string queryString = @"SELECT VALUE o FROM AdventureWorksEntities.SalesOrderHeaders AS o
WHERE o.OnlineOrderFlag = TRUE AND o.TotalDue > @ordercost";
// Define an ObjectQuery and pass the maxOrderCost parameter.
ObjectQuery<SalesOrderHeader> onlineOrders =
new ObjectQuery<SalesOrderHeader>(queryString, context);
onlineOrders.Parameters.Add(
new ObjectParameter("ordercost", orderCost));
// Print order information.
foreach (var onlineOrder in onlineOrders)
{
Console.WriteLine("Order ID: {0} Order date: "
+ "{1:d} Order number: {2}",
onlineOrder.SalesOrderID,
onlineOrder.OrderDate,
onlineOrder.SalesOrderNumber);
}
}
以下は、クエリ ビルダー メソッドの例です。
Using context As New AdventureWorksEntities()
' Specify the order amount.
Dim orderCost As Integer = 2500
' Define an ObjectQuery that returns only online orders
' more than the specified amount.
Dim onlineOrders As ObjectQuery(Of SalesOrderHeader) = _
context.SalesOrderHeaders.Where("it.OnlineOrderFlag = TRUE AND it.TotalDue > @ordercost", _
New ObjectParameter("ordercost", orderCost))
' Print order information.
For Each onlineOrder In onlineOrders
Console.WriteLine("Order ID: {0} Order date: {1:d} Order number: {2}", _
onlineOrder.SalesOrderID, onlineOrder.OrderDate, onlineOrder.SalesOrderNumber)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
// Specify the order amount.
int orderCost = 2500;
// Define an ObjectQuery that returns only online orders
// more than the specified amount.
ObjectQuery<SalesOrderHeader> onlineOrders =
context.SalesOrderHeaders
.Where("it.OnlineOrderFlag = TRUE AND it.TotalDue > @ordercost",
new ObjectParameter("ordercost", orderCost));
// Print order information.
foreach (var onlineOrder in onlineOrders)
{
Console.WriteLine("Order ID: {0} Order date: "
+ "{1:d} Order number: {2}",
onlineOrder.SalesOrderID,
onlineOrder.OrderDate,
onlineOrder.SalesOrderNumber);
}
}