Setting AutomationIdProperty on Buttons of ContentDialog

For the sake of Testing automation and also Accessibility, I'm trying to set the Windows.UI.Xaml.Automation.AutomationProperties.AutomationIdProperty on the buttons of a ContentDialog which is created programmatically.

Here is what I have tried:

    ContentDialog dialog = new ContentDialog()
    {
        Content = "This is my Content",
        Title = "This is my Title",
        PrimaryButtonText = "Primary Button",
        SecondaryButtonText = "Secondary Button",

    };
    // Don't know how to make this work
    Button primaryButton = closeDialog.FindName("PrimaryButton") as Button;
    if (primaryButton != null)
    {
            primaryButton.SetValue(Windows.UI.Xaml.Automation.AutomationProperties.AutomationIdProperty, "PrimaryCloseButton");
    }
    await dialog.ShowAsync();

My questions are: If there is a better, easier way to set the AutomationIdProperty? If not, can someone tell me how to make the above code work?