Control.Validating Event
Occurs when the control is validating.
[Visual Basic] Public Event Validating As CancelEventHandler [C#] public event CancelEventHandler Validating; [C++] public: __event CancelEventHandler* Validating;
[JScript] In JScript, you can handle the events defined by a class, but you cannot define your own.
Event Data
The event handler receives an argument of type CancelEventArgs containing data related to this event. The following CancelEventArgs property provides information specific to this event.
| Property | Description |
|---|---|
| Cancel | Gets or sets a value indicating whether the event should be canceled. |
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:
When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order:
If the CausesValidation property is set to false, the Validating and Validated events are suppressed.
If the Cancel property of the CancelEventArgs object is set to true in the Validating event delegate, all events that would normally occur after the Validating event are suppressed.
For more information about handling events, see Consuming Events.
Example
[Visual Basic, C#, C++] The following example uses the derived class TextBox and validates an e-mail address that the user enters. If the e-mail address is not in the standard format (containing "@" and "."), the validation fails, an ErrorProvider icon is displayed, and the event is canceled. This example assumes that a TextBox and ErrorProvider control have been created on a form.
[Visual Basic] 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 = "E-mail address is required." Return False End If ' Confirm that there is an "@" and a "." in the e-mail 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 = "E-mail address must be valid e-mail address format." + ControlChars.Cr + _ "For example 'someone@example.com' " 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 [C#] 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 e-mail address string is not empty. if(emailAddress.Length == 0) { errorMessage = "e-mail address is required."; return false; } // Confirm that there is an "@" and a "." in the e-mail address, and in the correct order. if(emailAddress.IndexOf("@") > -1) { if(emailAddress.IndexOf(".", emailAddress.IndexOf("@") ) > emailAddress.IndexOf("@") ) { errorMessage = ""; return true; } } errorMessage = "e-mail address must be valid e-mail address format.\n" + "For example 'someone@example.com' "; return false; } [C++] 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, S""); } public: bool ValidEmailAddress(String* emailAddress, [Out] String** errorMessage) { // Confirm that the e-mail address String* is not empty. if (emailAddress->Length == 0) { *errorMessage = S"e-mail address is required."; return false; } // Confirm that there is an S"@" and a S"." in the e-mail address, and in the correct order. if (emailAddress->IndexOf(S"@") > -1) { if (emailAddress->IndexOf(S".", emailAddress->IndexOf(S"@")) > emailAddress->IndexOf(S"@")) { *errorMessage = S""; return true; } } *errorMessage = S"e-mail address must be valid e-mail address format.\n For example 'someone@example.com' "; return false; }
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Requirements
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
See Also
Control Class | Control Members | System.Windows.Forms Namespace | OnValidating | CausesValidation | Validated