sql exeption was not handled by user code : 

        if (Page.IsValid)
        {
            DataSet.UsersDataTable oUserDataTable =
                new DataSet.UsersDataTable();

            DataSetTableAdapters.UsersTableAdapter oUserTableAdapter =
                new DataSetTableAdapters.UsersTableAdapter();

            oUserTableAdapter.FillUserByUserName(oUserDataTable, txtUserName.Text);

            if (oUserDataTable.Count!=1)
            {
                string strErrorMessage =
                    "UserName Or Password Is Not Correct ! Please Try Again . . . ";
                DisplayErrorMessage(strErrorMessage);
                return;
            }

            DataSet.UsersRow oUserRow = oUserDataTable[0];

            if (string.Compare(oUserRow.Password.Trim(),txtPassword.Text.Trim(),false)!=0)
            {
                 string strErrorMessage =
                    "UserName Or Password Is Not Correct ! Please Try Again . . . ";
                 DisplayErrorMessage(strErrorMessage);
                return;
            }

            if (oUserRow.IsUserActive==false)
            {
                string strInformationMessage =
                    string.Format("Dear {0} You Should Not Login At This Time , Please Contact Support",txtUserName.Text);
                DisplayInformationMessage(strInformationMessage);
                return;
            }


Additional information: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)


