How to validate null Value?

Question

My Source code is SQl = select ActiveRate from co_batchwiserate where batchid =' + CrsList.GetBatchID.ToString().Trim() + ' and delstate 1; SqlCommand cmd = new SqlCommand(SQl SCon.GetConn()); strValue = (string)cmd.ExecuteScalar(); validate Stvalue is null or empty means validate this strvalue if (strValue == null) { LblErr.Text = Invalid Course Amount; return; }

Vulpes · Answer

I think you'll get back DBNull.Value rather than null if there's no match for that query but you can check for both or an empty string as follows: object obj = cmd.ExecuteScalar(); if (Convert.IsDBNull(obj) || obj == null || obj.ToString() == ) { LblErr.Text = Invalid Course Amount; return; } else { strValue = obj.ToString(); // do something with strValue }