Expose a Server-side UI Automation Provider

This topic contains example code that shows how to expose a server-side UI Automation provider that is hosted in a System.Windows.Forms.Control window.

The example overrides the window procedure to trap WM_GETOBJECT, which is the message sent by the UI Automation core service when a client application requests information about the window.

Example

/// <summary>
/// Handles WM_GETOBJECT message; others are passed to base handler.
/// </summary>
/// <param name="m">Windows message.</param>
/// <remarks>
/// This method enables UI Automation to find the control.
/// In this example, the implementation of IRawElementProvider is in the same class
/// as this method.
/// </remarks>
protected override void WndProc(ref Message m)
{
    const int WM_GETOBJECT = 0x003D;

    if ((m.Msg == WM_GETOBJECT) && (m.LParam.ToInt32() == 
        AutomationInteropProvider.RootObjectId))
    {
        m.Result = AutomationInteropProvider.ReturnRawElementProvider(
                this.Handle, m.WParam, m.LParam, 
                (IRawElementProviderSimple)this);
        return;
    }
    base.WndProc(ref m);
}

''' <summary>
''' Handles WM_GETOBJECT message; others are passed to base handler.
''' </summary>
''' <param name="m">Windows message.</param>
''' <remarks>
''' This method enables UI Automation to find the control.
''' In this example, the implementation of IRawElementProvider is in the same class
''' as this method.
''' </remarks>
Protected Overrides Sub WndProc(ByRef m As Message)
    Const WM_GETOBJECT As Integer = &H3D

    If m.Msg = WM_GETOBJECT AndAlso m.LParam.ToInt32() = AutomationInteropProvider.RootObjectId Then
        m.Result = AutomationInteropProvider.ReturnRawElementProvider(Me.Handle, m.WParam, m.LParam, DirectCast(Me, IRawElementProviderSimple))
        Return
    End If
    MyBase.WndProc(m)

End Sub 'WndProc

See Also

Concepts

UI Automation Providers Overview
Server-Side UI Automation Provider Implementation