Control.BeginInvoke Method (Delegate, Object)
Assembly: System.Windows.Forms (in system.windows.forms.dll)
'Declaration Public Function BeginInvoke ( _ method As Delegate, _ ParamArray args As Object() _ ) As IAsyncResult 'Usage Dim instance As Control Dim method As Delegate Dim args As Object() Dim returnValue As IAsyncResult returnValue = instance.BeginInvoke(method, args)
public final function BeginInvoke ( method : Delegate, ... args : Object ) : IAsyncResult
A delegate to a method that takes parameters of the same number and type that are contained in the args parameter.
An array of objects to pass as arguments to the given method. This can be a null reference (Nothing in Visual Basic) if no arguments are needed.
Return ValueAn IAsyncResult that represents the result of the BeginInvoke operation.
The delegate is called asynchronously, and this method returns immediately. You can call this method from any thread, even the thread that owns the control's handle. If the control's handle does not exist yet, this method searches up the control's parent chain until it finds a control or form that does have a window handle. If no appropriate handle can be found, BeginInvoke will throw an exception. Exceptions within the delegate method are considered untrapped and will be sent to the application's untrapped exception handler.
Most methods on a control can only be called from the thread where the control was created. In addition to the InvokeRequired property, there are four methods on a control that are thread safe: Invoke, BeginInvoke, EndInvoke, and CreateGraphics. For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread. The invoke methods always invoke their callbacks on the control's thread.
An exception might be thrown if the thread that should process the message is no longer active.
The following code example demonstrates a use of the BeginInvoke method.
Delegate Sub MyDelegate(myControl As Label, myArg2 As String) Private Sub Button_Click(sender As Object, e As EventArgs) Dim myArray(1) As Object myArray(0) = New Label() myArray(1) = "Enter a Value" myTextBox.BeginInvoke(New MyDelegate(AddressOf DelegateMethod), myArray) End Sub 'Button_Click Public Sub DelegateMethod(myControl As Label, myCaption As String) myControl.Location = New Point(16, 16) myControl.Size = New Size(80, 25) myControl.Text = myCaption Me.Controls.Add(myControl) End Sub 'DelegateMethod
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.