سوال فى c#

قم بعمل Query

Create Procedure AddUniqueProduct
(
  @ProductName NVarchar( 80 ),
  @UnitPrice Money
)
As
If Exists
  (
  Select ProductName
  From Products
  Where ProductName = @ProductName
  )
  Return 1
Else
  Insert Products ( ProductName, UnitPrice )
  Values ( @ProductName, @UnitPrice )

ثم استخدم هذا الكود

SqlConnection northCon;
SqlCommand cmd;
SqlParameter paramReturn;

northCon = new SqlConnection (@" Server = localhost; Integrated security = SSPI; DataBase = Northwind");
cmd = new SqlCommand ( " AddUniqueProduct", northCon);
cmd.CommandType = CommandType.StoredProcedure;
paramReturn= cmd.Parameters.Add("ReturnValue" , SqlDBType.Int);
paramReturn.Direction = ParameterDirection.ReturnValue;
cmd.Parameters.Add("@ProductName" , "Milk");
cmd.Parameters.Add(" @UnitPrice" , 12.5);
northCon.Open();
cmd.executeNonQuery();
If ( (int)cmd.Parameters["ReturnValue"].Value == 0 )
{
MessageBox.Show ( " New Product Added ");

}
else
{
MessageBox.Show (" Product already EXISTS!");
}
northCon.Close();