private void btnAdd_Click(object sender, RoutedEventArgs e) { List <string> errors = new List <string>(); if (string.IsNullOrEmpty(txtFirstName.Text)) { errors.Add("FirstName is required."); } ; if (string.IsNullOrEmpty(txtLastName.Text)) { errors.Add("LastName is required."); } ; if (string.IsNullOrEmpty(txtAddress.Text)) { errors.Add("Address is required."); } ; if (string.IsNullOrEmpty(txtSex.Text)) { errors.Add("Sex is required."); } ; if (string.IsNullOrEmpty(txtContactNumber.Text)) { errors.Add("Contact-Number is required."); } ; if (string.IsNullOrEmpty(txtEmail.Text)) { errors.Add("Email is required."); } ; if (string.IsNullOrEmpty(txtPassword.Text)) { errors.Add("Password is required."); } ; if (errors.Count > 0) { foreach (var error in errors) { txtError.Text = txtError.Text + error + "\n"; } return; } var op = Userbll.Add(new User() { UserID = Guid.NewGuid(), FirstName = txtFirstName.Text, LastName = txtLastName.Text, Address = txtAddress.Text, Sex = txtSex.Text, ContactNumber = txtContactNumber.Text, Email = txtEmail.Text, Password = txtPassword.Text }); if (op.Code != "200") { MessageBox.Show("Error : " + op.Message); } else { MessageBox.Show(" is successfully added to table"); } this.Close(); }