AxHost.SetAboutBoxDelegate(AxHost+AboutBoxDelegate) Method


Calls the ShowAboutBox() method to display the ActiveX control's About dialog box.

 void SetAboutBoxDelegate(System::Windows::Forms::AxHost::AboutBoxDelegate ^ d);
protected void SetAboutBoxDelegate (System.Windows.Forms.AxHost.AboutBoxDelegate d);
member this.SetAboutBoxDelegate : System.Windows.Forms.AxHost.AboutBoxDelegate -> unit
Protected Sub SetAboutBoxDelegate (d As AxHost.AboutBoxDelegate)



The following code example overrides the constructor, and the SetAboutBoxDelegate and AttachInterfaces methods of an AxHost derived class that wraps the Microsoft Masked Edit ActiveX Control. This code requires that you have created the generated source code by running the AxImp.exe on the MSMask32.ocx file with the /source switch to generate the wrapper class to be edited. This code is only shown in C# syntax because that is the only language output by the AxImp.exe.

public AxMaskEdBox()
  base("c932ba85-4374-101b-a56c-00aa003668dc") // The ActiveX control's class identifier.
    // Make the AboutBox method the about box delegate.
    this.SetAboutBoxDelegate(new AboutBoxDelegate(AboutBox));

public virtual void AboutBox()
    // If the instance of the ActiveX control is null when the AboutBox method
    // is called, raise an InvalidActiveXStateException exception.
    if ((this.ocx == null))
        throw new System.Windows.Forms.AxHost.InvalidActiveXStateException(
          "AboutBox", System.Windows.Forms.AxHost.ActiveXInvokeKind.MethodInvoke);
    // Show the about box if the ActiveX control has one.
    if (this.HasAboutBox)

protected override void AttachInterfaces()
        // Attach the IMSMask interface to the ActiveX control.
        this.ocx = ((MSMask.IMSMask)(this.GetOcx()));
    catch (System.Exception ex)


The SetAboutBoxDelegate method also allows derived classes to handle the ShowAboutBox method without attaching a delegate. This is the preferred technique for handling the ShowAboutBox method in a derived class.

Notes to Inheritors

When overriding SetAboutBoxDelegate(AxHost+AboutBoxDelegate) in a derived class, be sure to call the base class's SetAboutBoxDelegate(AxHost+AboutBoxDelegate) method so that registered delegates receive the ShowAboutBox() method.

Applies to

See also