Control.Validating Event

public:
 event System::ComponentModel::CancelEventHandler ^ Validating;

public event System.ComponentModel.CancelEventHandler Validating;

public event System.ComponentModel.CancelEventHandler? Validating;

member this.Validating : System.ComponentModel.CancelEventHandler 

Public Custom Event Validating As CancelEventHandler 

Event Type

Examples

The following code example uses the derived class TextBox and validates an email address that the user enters. If the email address is not in the standard format (containing "@" and "."), the validation fails, an ErrorProvider icon is displayed, and the event is canceled. This example requires that a TextBox and ErrorProvider control have been created on a form.

private:
   void textBox1_Validating( Object^ sender, System::ComponentModel::CancelEventArgs^ e )
   {
      String^ errorMsg;
      if ( !ValidEmailAddress( textBox1->Text, &errorMsg ) )
      {
         // Cancel the event and select the text to be corrected by the user.
         e->Cancel = true;
         textBox1->Select( 0, textBox1->Text->Length );
         
         // Set the ErrorProvider error with the text to display.
         this->errorProvider1->SetError( textBox1, errorMsg );
      }
   }

   void textBox1_Validated( Object^ sender, System::EventArgs^ e )
   {
      // If all conditions have been met, clear the ErrorProvider of errors.
      errorProvider1->SetError( textBox1, "" );
   }

public:
   bool ValidEmailAddress( String^ emailAddress, [Out]interior_ptr<String^> errorMessage )
   {
      // Confirm that the email address String* is not empty.
      if ( emailAddress->Length == 0 )
      {
         *errorMessage = "email address is required.";
         return false;
      }

      // Confirm that there is an "@" and a "." in the email address, and in the correct order.
      if ( emailAddress->IndexOf( "@" ) > -1 )
      {
         if ( emailAddress->IndexOf( ".", emailAddress->IndexOf( "@" ) ) > emailAddress->IndexOf( "@" ) )
         {
            *errorMessage = "";
            return true;
         }
      }

      *errorMessage = "email address must be valid email address format.\n" +
         "For example '[email protected]' ";
      return false;
   }

private void textBox1_Validating(object sender, 
                System.ComponentModel.CancelEventArgs e)
{
   string errorMsg;
   if(!ValidEmailAddress(textBox1.Text, out errorMsg))
   {
      // Cancel the event and select the text to be corrected by the user.
      e.Cancel = true;
      textBox1.Select(0, textBox1.Text.Length);

      // Set the ErrorProvider error with the text to display. 
      this.errorProvider1.SetError(textBox1, errorMsg);
   }
}

private void textBox1_Validated(object sender, System.EventArgs e)
{
   // If all conditions have been met, clear the ErrorProvider of errors.
   errorProvider1.SetError(textBox1, "");
}
public bool ValidEmailAddress(string emailAddress, out string errorMessage)
{
   // Confirm that the email address string is not empty.
   if(emailAddress.Length == 0)
   {
      errorMessage = "email address is required.";
         return false;
   }

   // Confirm that there is an "@" and a "." in the email address, and in the correct order.
   if(emailAddress.IndexOf("@") > -1)
   {
      if(emailAddress.IndexOf(".", emailAddress.IndexOf("@") ) > emailAddress.IndexOf("@") )
      {
         errorMessage = "";
         return true;
      }
   }
   
   errorMessage = "email address must be valid email address format.\n" +
      "For example '[email protected]' ";
      return false;
}

   Private Function ValidEmailAddress(ByVal emailAddress As String, ByRef errorMessage As String) As Boolean
      ' Confirm there is text in the control.
      If textBox1.Text.Length = 0 Then
         errorMessage = "Email address is required."
         Return False

      End If

      ' Confirm that there is an "@" and a "." in the email address, and in the correct order.
      If emailAddress.IndexOf("@") > -1 Then
         If (emailAddress.IndexOf(".", emailAddress.IndexOf("@")) > emailAddress.IndexOf("@")) Then
            errorMessage = ""
            Return True
         End If
      End If

      errorMessage = "Email address must be valid email address format." + ControlChars.Cr + _
        "For example '[email protected]' "
      Return False
End Function

   Private Sub textBox1_Validating(ByVal sender As Object, _
   ByVal e As System.ComponentModel.CancelEventArgs) Handles textBox1.Validating

      Dim errorMsg As String
      If Not ValidEmailAddress(textBox1.Text, errorMsg) Then
         ' Cancel the event and select the text to be corrected by the user.
         e.Cancel = True
         textBox1.Select(0, textBox1.Text.Length)

         ' Set the ErrorProvider error with the text to display. 
         Me.errorProvider1.SetError(textBox1, errorMsg)
      End If
   End Sub


   Private Sub textBox1_Validated(ByVal sender As Object, _
   ByVal e As System.EventArgs) Handles textBox1.Validated
      ' If all conditions have been met, clear the error provider of errors.
      errorProvider1.SetError(textBox1, "")
   End Sub

Remarks

When you change the focus by using the keyboard (TAB, SHIFT+TAB, and so on), by calling the Select or SelectNextControl methods, or by setting the ContainerControl.ActiveControl property to the current form, focus events occur in the following order:

1. Enter

2. GotFocus

3. Leave

4. Validating

5. Validated

6. LostFocus

When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order:

1. Enter

2. GotFocus

3. LostFocus

4. Leave

5. Validating

6. Validated

If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

If the Cancel property of the CancelEventArgs is set to true in the Validating event delegate, all events that would usually occur after the Validating event are suppressed.

For more information about handling events, see Handling and Raising Events.

Applies to

See also

• OnValidating(CancelEventArgs)
• CausesValidation
• Validated