Occurs when the control is validating.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
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:
Do not attempt to set focus from within the Enter, GotFocus, Leave, LostFocus, , or Validated event handlers. Doing so can cause your application or the operating system to stop responding. For more information, see the WM_KILLFOCUS topic in the "Keyboard Input Reference" section, and the "Message Deadlocks" section of the "About Messages and Message Queues" topic in the MSDN library at http://msdn.microsoft.com/library.
For more information about handling events, see Consuming Events.
The following code 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 requires that a TextBox and ErrorProvider control have been created on a form.
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 'firstname.lastname@example.org' " 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
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.