Question

I have a large WPF application where I have a datagrid within a user control and I need to create an override for OnCreateAutomationPeer. I am having trouble doing that and the event never seems to fire. In my code-behind I have something similar to

public partial class DocChecklistView :  UserControl, IDataModuleView {     

        protected override System.Windows.Automation.Peers.AutomationPeer OnCreateAutomationPeer()
        {                
            return null;
        }

        public CDocumentChecklistView() {
            InitializeComponent();
        }
}

The XAML is pretty standard with code like

<UserControl>
 <Grid>
        <toolkit:DataGrid  ItemsSource="{Binding Source={StaticResource DocumentsVS}}" AutoGenerateColumns="False" CanUserAddRows="False" CanUserDeleteRows="False"
                FontSize="16" Name="_dgDocuments" Style="{StaticResource EklektosDataGridStyle}" . . . >
</UserControl>

And in the above, the toolkit:DataGrid is set to the namespace for the WPFToolkit. The DataGrid works as designed, I’ve just never done an override within a user control and the code I have above never fires – a breakpoint there is never reached.

Any thoughts?

Answer 1

You have override the method correctly. In case you want to override the OnCreateAutomationPeer of your dataGrid, you have to subclass the DataGrid–

public class MyDataGrid : DataGrid
{
    protected override AutomationPeer OnCreateAutomationPeer()
    {
        return null;
    }
}

And in xaml, use your custom dataGrid

<local:MyDataGrid x:Name="dataGrid"/>

And in constructor of your UserControl –

public CDocumentChecklistView()
{
    InitializeComponent();
    AutomationPeer a = UIElementAutomationPeer.CreatePeerForElement(dataGrid);
}

You need to ask for AutomationPeer to hit the breakpoint. Isn’t it how you desired it?

This is what you missing – UIElementAutomationPeer.CreatePeerForElement(dataGrid);