private bool CheckData() { if (txt_UserId.Text.Trim().Equals(string.Empty)) { MessageBox.Show("Please Input the User ID", "Prompt", MessageBoxButtons.OK, MessageBoxIcon.Warning); txt_UserId.Focus(); return(false); } if (false == ConvertObject.IsInt(txt_UserId.Text.Trim())) { MessageBox.Show("User ID can only enter a number", "Prompt", MessageBoxButtons.OK, MessageBoxIcon.Warning); txt_UserId.Focus(); return(false); } foreach (ListViewItem lvi in lvw_UserList.Items) { if (txt_UserId.Text.Trim().Equals(lvi.SubItems[1].Text)) { MessageBox.Show("The user ID already exists, please modify", "Prompt", MessageBoxButtons.OK, MessageBoxIcon.Warning); txt_UserId.Focus(); return(false); } } if (txt_UserName.Text.Trim().Equals(string.Empty)) { MessageBox.Show("Please input the user name", "Prompt", MessageBoxButtons.OK, MessageBoxIcon.Warning); txt_UserName.Focus(); return(false); } return(true); }