在VB.Net中使用实体框架利用存储过程的返回值

Question

I hope the below stored procedure inserts a new record to the table and returns the same when executed. I tried to utilize this stored procedure from Entity Framework as shown far below. The new record is properly inserted. But I don't know why I couldn't get the value returned from the procedure.

Stored Procedure:

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 Code:

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

When I try this code, I get the following error

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

at the line Dim mat As Material = CType(element, Material)

Answer 1

It is very clear from exception that you are casting and object of Stored_Procedure_Test.insertQuery_Result to object type of Material . Your SP returns collection of objects which are of type Stored_Procedure_Test.insertQuery_Result . So what you can do is get value from the object returned by SP like this.

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;

So your complete code should look like this

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