HOW TO：使用對應多個結果圖案的預存程序 (LINQ to SQL)

更新： November 2007

如果預存程序 (Stored Procedure) 可以傳回多個結果圖案，則傳回型別不可以強型別 (Strongly Typed) 為單一投影圖案。雖然 LINQ to SQL 可以產生所有可能的投影型別，但是無法得知它們傳回的順序。

請將這個案例與循序產生多個結果圖案的預存程序案例比較。如需詳細資訊，請參閱 HOW TO：使用對應循序結果圖案的預存程序 (LINQ to SQL)。

ResultTypeAttribute 屬性 (Attribute) 會套用至傳回多個結果型別的預存程序，以指定程序可以傳回的型別集。

範例

在下列 SQL 程式碼範例中，結果圖案會根據輸入 (shape =1 或 shape = 2) 而不同。您無法得知會先傳回哪個投影。

CREATE PROCEDURE VariableResultShapes(@shape int)
AS
if(@shape = 1)
    select CustomerID, ContactTitle, CompanyName from customers
else if(@shape = 2)
    select OrderID, ShipName from orders

<FunctionAttribute(Name:="dbo.VariableResultShapes"), _
ResultType(GetType(VariableResultShapesResult1)), _
ResultType(GetType(VariableResultShapesResult2))> _
Public Function VariableResultShapes(<Parameter(DbType:="Int")> ByVal shape As System.Nullable(Of Integer)) As IMultipleResults
    Dim result As IExecuteResult = Me.ExecuteMethodCall(Me, CType(MethodInfo.GetCurrentMethod, MethodInfo), shape)
    Return CType(result.ReturnValue, IMultipleResults)
End Function

 [Function(Name="dbo.VariableResultShapes")]
    [ResultType(typeof(VariableResultShapesResult1))]
    [ResultType(typeof(VariableResultShapesResult2))]
    public IMultipleResults VariableResultShapes([Parameter(DbType="Int")] System.Nullable<int> shape)
    {
        IExecuteResult result = this.ExecuteMethodCall(this, ((MethodInfo)(MethodInfo.GetCurrentMethod())), shape);
        return ((IMultipleResults)(result.ReturnValue));
    }

您可使用類似下列的程式碼來執行此預存程序。

注意事項：
您必須使用 GetResult<TElement> 模式，根據您對預存程序的了解以取得正確型別的列舉值。

Dim db As New Northwnd("c:\northwnd.mdf")

' Assign the results of the procedure with an argument
' of (1) to local variable 'result'.
Dim result As IMultipleResults = db.VariableResultShapes(1)

' Iterate through the list and write results (the company name)
' to the console.
For Each compName As VariableResultShapesResult1 _
    In result.GetResult(Of VariableResultShapesResult1)()
    Console.WriteLine(compName.CompanyName)
Next

' Pause to view company names; press Enter to continue.
Console.ReadLine()

' Assign the results of the procedure with an argument
' of (2) to local variable 'result.'
Dim result2 As IMultipleResults = db.VariableResultShapes(2)

' Iterate through the list and write results (the order IDs)
' to the console.
For Each ord As VariableResultShapesResult2 _
    In result2.GetResult(Of VariableResultShapesResult2)()
    Console.WriteLine(ord.OrderID)
Next

Northwnd db = new Northwnd(@"c:\northwnd.mdf");

// Assign the results of the procedure with an argument
// of (1) to local variable 'result'.
IMultipleResults result = db.VariableResultShapes(1);

// Iterate through the list and write results (the company names)
// to the console.
foreach(VariableResultShapesResult1 compName in
    result.GetResult<VariableResultShapesResult1>())
{
    Console.WriteLine(compName.CompanyName);
}

// Pause to view company names; press Enter to continue.
Console.ReadLine();

// Assign the results of the procedure with an argument
// of (2) to local variable 'result'.
IMultipleResults result2 = db.VariableResultShapes(2);

// Iterate through the list and write results (the order IDs)
// to the console.
foreach (VariableResultShapesResult2 ord in
    result2.GetResult<VariableResultShapesResult2>())
{
    Console.WriteLine(ord.OrderID);
}

請參閱

其他資源

預存程序 (LINQ to SQL)