My code works on Both Emulators: oreo and marshmallow.

button.Click += (o, e) =>
            {
                try
                {
                    SqlConnection sqlConnection = new SqlConnection(connectionString);
                    string select = "Select * From [dbo].[bma_users] Where username = '" + name.Text + "'";
                    SqlCommand sqlCommand = new SqlCommand(select, sqlConnection);
                    sqlConnection.Open();
                    SqlDataReader dr = sqlCommand.ExecuteReader();

                    if (dr.HasRows == true)
                    {
                        StartActivity(typeof(LandingPage));
                    }
                    else
                    {
                        result.Text = "Failure";
                    }

                    sqlConnection.Close();
                }
                catch(SqlException ex)
                {
                    foreach(var error in ex.Errors)
                    {
                        Console.WriteLine("Found an exception {0}:", error);
                    }
                   
                }

As I said this works on emulators but not on the TC20.

07-20 13:13:36.587 I/mono-stdout(24804): Found an exception System.Data.SqlClient.SqlError: Snix_Connect (provider: SNI_PN7, error: 40 - SNI_ERROR_40):
Found an exception System.Data.SqlClient.SqlError: Snix_Connect (provider: SNI_PN7, error: 40 - SNI_ERROR_40):
07-20 13:13:36.593 I/Choreographer(24804): Skipped 1006 frames!  The application may be doing too much work on its main thread.

Any help would be greatly appreciated. Thanks in advance.