What is the cause of the error ?

Question

i want to read the data table and the previous value of a field, the value I add ...

But it gives the following error:

In relation to the connection ! 

 

http://s4.picofile.com/file/8166859342/1errror_mojodi.jpg 

 

i use this code :

 

 int a = 0;

            try

            {

                SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=Shopping;Integrated Security=True");

                SqlCommand com = new SqlCommand();

                com.CommandText = "SELECT TOP 1 Mojodi FROM TMojojdi ORDER BY Id DESC";

                con.Open();

                SqlDataReader dr = com.ExecuteReader();

                if (dr.Read())

                {

                    a = Int32.Parse(dr[0].ToString());

                }

                con.Close();

            }

            catch

            {

            }