在VB.Net中使用實體框架利用存儲過程的返回值

Question

我希望下面的存儲過程在表中插入一條新記錄，並在執行時返回相同的記錄。 我試圖利用實體框架中的該存儲過程，如下所示。 新記錄已正確插入。 但是我不知道為什么我無法從過程中返回值。

存儲過程：

USE [Materials]
GO

CREATE PROCEDURE [dbo].[insertQuery1]
@Code NVARCHAR(50),
@Name NVARCHAR(100)
AS
BEGIN
INSERT INTO dbo.Materials
(Code, Name)

Values (@Code, @Name)

Select mat.ID, mat.Code, mat.Name from dbo.Materials mat where mat.ID = SCOPE_IDENTITY()

END

ASPX.VB代碼：

Protected Sub testing_Click(sender As Object, e As EventArgs)
    Dim code As String
    Dim name As String
    Dim element As Object
    code = "New Code"
    name = "New Element"
    element = ent.insertQuery(code, name)
    Dim mat As Material = CType(element, Material)
End Sub

當我嘗試此代碼時，出現以下錯誤

Unable to cast object of type 'System.Data.Objects.ObjectResult`1[Stored_Procedure_Test.insertQuery_Result]' to type 'Stored_Procedure_Test.Material'.

在線Dim mat As Material = CType(element, Material)

Answer 1

從異常非常清楚，您正在將Stored_Procedure_Test.insertQuery_Result的對象Stored_Procedure_Test.insertQuery_Result轉換為Material對象類型。 您的SP返回類型為Stored_Procedure_Test.insertQuery_Result的對象的Stored_Procedure_Test.insertQuery_Result 。 因此，您可以做的就是從SP這樣返回的對象中獲取價值。

Stored_Procedure_Test.insertQuery_Result element = ent.insertQuery(code, name).FirstOrDefault();
//And you can access properties of this object like this
string name=element.Name;

因此，您的完整代碼應如下所示

Protected Sub testing_Click(sender As Object, e As EventArgs)
Dim code As String
Dim name As String
code = "New Code"
name = "New Element"
Dim element As Stored_Procedure_Test.insertQuery_Result = ent.insertQuery(code, name).FirstOrDefault();

//Now you can directly use the `element` to access values returned from SP.
End Sub