stored procedures returning error "Object must implement IConvertible"

Hi,

I'm creating my first app using web forms and asp.net. I followed the examples in the book for executing a stored procedure, but I always get the "Object must implement IConvertible" error.

Some background:

The stored procedure returns @@error

Here's the code...


Imports System.Data
Imports System.Data.SqlClient
Imports System.Convert

Public Class WebForm1

Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click

Dim cn As New SqlConnection(sqlConnectString)
cn.Open()

Dim sql As String = "Login"

Dim cmd As New SqlCommand(sql, cn)
cmd.CommandType = CommandType.StoredProcedure

'define return value
With cmd.Parameters.Add("@RETVAL", SqlDbType.Int)
.Direction = ParameterDirection.ReturnValue
End With


'first parameter
With cmd.Parameters.Add("@UserName", SqlDbType.NVarChar)
.Size = 10
.Direction = ParameterDirection.Input
.Value = txtUserName
End With

'second parameter
With cmd.Parameters.Add("@Password", SqlDbType.NVarChar)
.Size = 10
.Direction = ParameterDirection.Input
.Value = txtPassword
End With

'WHICH METHOD SHOULD BE USED?

' Dim dr As SqlDataReader = cmd.ExecuteReader()

Dim result As Integer = cmd.ExecuteNonQuery()

cn.Close()

End Sub
End Class

Thanks in advance