Getting return value from stored procedure in ADO.NET

Just tried on my box and this works for me:

In SQL Server:

DROP PROCEDURE TestProc;
GO
CREATE PROCEDURE TestProc
AS
   RETURN 123;
GO

In C#

        string cnStr = "Server=.;Database=Sandbox;Integrated Security=sspi;";
        using (SqlConnection cn = new SqlConnection(cnStr)) {
            cn.Open();
            using (SqlCommand cmd = new SqlCommand("TestProc", cn)) {
                cmd.CommandType = CommandType.StoredProcedure;
                SqlParameter returnValue = new SqlParameter();
                returnValue.Direction = ParameterDirection.ReturnValue;
                cmd.Parameters.Add(returnValue);

                cmd.ExecuteNonQuery();
                Assert.AreEqual(123, (int)returnValue.Value);
            }
        }

Do you get the value of you EXEC in TSQL? I wonder if refactoring the TSQL would help (and using SCOPE_IDENTITY():

so change:

COMMIT TRAN T1
RETURN @@IDENTITY

to:

SET @auctionID = SCOPE_IDENTITY()
COMMIT TRAN T1
RETURN @auctionID

(I would also change the other @@IDENTITY to SCOPE_IDENTITY())

---

As a minor optimisation, you could also use:

return (int)retval.Value;

but this side of things should have worked "as is" from what I can see (hence why I'm focusing on the TSQL).

Some one can also use this simple and short method to calculate return value from SP

In SQL:

Create Table TestTable 
(
 Int Id
)

CREATE PROCEDURE Proc_TestProc
 @Id
 AS
   Begin
     Set NOCOUNT ON  //Use this line if you don't want to return any message from SQL

     Delete from TestTable where Id = @Id
     return 1

     Set NOCOUNT OFF //NOCOUNT OFF is Optional for NOCOUNT ON property
   End

Sql Server always returns Int type value only.

and in C#

using (SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["TestConnectionString"].ToString()))
using (SqlCommand cmd = new SqlCommand("Proc_TestProc", conn))
{
 cmd.CommandType = CommandType.StoredProcedure;

 cmd.Parameters.AddWithValue("@Id", 1);
 var returnParameter = cmd.Parameters.Add("@ReturnVal", SqlDbType.Int);
 returnParameter.Direction = ParameterDirection.ReturnValue;

 conn.Open();
 cmd.ExecuteNonQuery();
 var result = returnParameter.Value;
}

You can also check your return value in SQL by using this command:

DECLARE @return_status int;
EXEC @return_status = dbo.[Proc_TestProc] 1;
SELECT 'Return Status' = @return_status;
print 'Returned value from Procedure: ' + Convert(varchar, @return_status); // Either previous or this line both will show you the value of returned value

I solved the problem: you have to set SqlCommand.CommandType to CommandType.StoredProcedure in order to get return values and/or output parameters. I haven't found any documentation about that, but now everything works.