Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
The MaskedTextBox control will optionally validate user input against the type defined by its MaskedTextBox.ValidatingType property. When this property is not null, the following series of events occurs:
The validation sequence begins when one of the following occurs:
Any of these events result in a call to the Parse method of the type specified with the ValidatingType property. Parse is responsible for the conversion of the formatted input string to the target type. A successful conversion equates to a successful validation.
After the event handler for the Validating, is raised. A handler can be implemented to perform standard validation, perhaps including canceling the event.event returns, the standard validation event,
If the event is not canceled in step 3, the standard control validation event Validated is raised.
If the Cancel property is set to true in the event handler, the event will be canceled and the MaskedTextBox control retains focus, unless the subsequent Validating event sets its version of the CancelEventArgs.Cancel property back to false.
The following code example attempts to parse the user's input as a valid DateTime object. If it fails, the event handler displays an error message to the user. If the value is a valid DateTime, the code verifies that the date supplied is not prior to today's date. This code example requires that your Windows Forms project contains a MaskedTextBox control named MaskedTextBox1 and a ToolTip control named ToolTip1.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Me.MaskedTextBox1.Mask = "00/00/0000" Me.MaskedTextBox1.ValidatingType = GetType(System.DateTime) Me.ToolTip1.IsBalloon = True End Sub Private Sub MaskedTextBox1_TypeValidationCompleted(ByVal sender As Object, ByVal e As TypeValidationEventArgs) Handles MaskedTextBox1.TypeValidationCompleted If (Not e.IsValidInput) Then Me.ToolTip1.ToolTipTitle = "Invalid Date" Me.ToolTip1.Show("The data you supplied must be a valid date in the format mm/dd/yyyy.", Me.MaskedTextBox1, 0, -20, 5000) Else ' Now that the type has passed basic type validation, enforce more specific type rules. Dim UserDate As DateTime = CDate(e.ReturnValue) If (UserDate < DateTime.Now) Then Me.ToolTip1.ToolTipTitle = "Invalid Date" Me.ToolTip1.Show("The date in this field must be greater than today's date.", Me.MaskedTextBox1, 0, -20, 5000) e.Cancel = True End If End If End Sub ' Hide the tooltip if the user starts typing again before the five-second display limit on the tooltip expires. Private Sub MaskedTextBox1_KeyDown(ByVal sender As Object, ByVal e As KeyEventArgs) Handles MaskedTextBox1.KeyDown Me.ToolTip1.Hide(Me.MaskedTextBox1) End Sub
Available since 2.0