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Code: Overriding Control Validation on Windows Forms in the Closing Event (Visual Basic)

Visual Studio .NET 2003

This example shows how to close a form even if there is validation logic in the form and one or more of the controls contain invalid data. In the example, there is validation logic for a TextBox control. Validation is overridden in the form's Closing event.

Example

Private Sub TextBox1_Validating(ByVal sender As Object, _
    ByVal e As System.ComponentModel.CancelEventArgs) _ 
    Handles TextBox1.Validating
    If TextBox1.Text.Length < 8 Then
            ("Value you entered is not valid;" _
            & " it must be at least 8 characters.")
        e.Cancel = True
    End If
End Sub

Private Sub Form1_Closing(ByVal sender As Object, _
    ByVal e As System.ComponentModel.CancelEventArgs) _ 
    Handles MyBase.Closing
    e.Cancel = False
End Sub

Compiling the Code

This project requires:

  • A reference to the System namespace.
  • A Windows Form.
  • A TextBox control named TextBox1.
  • Another control on the form that can receive focus to illustrate validation being overridden.

Security

User input into a Windows Forms can include potentially invalid, malformed, or malicious information. Always check that the values that a user enters conform to the requirements for your application before using the values.

See Also

Code: Validating User Input on Windows Forms (Visual Basic) | Validation of Control Data on Windows Forms | Form.Closing Event | CancelEventArgs Class | Windows Applications Example Topics

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