Where is Button.DialogResult in WPF?

In System.Windows.Forms.Button there is a property DialogResult, where is this property in the System.Windows.Controls.Button (WPF)?

There is no built-in Button.DialogResult, but you can create your own (if you like) using a simple attached property:

public class ButtonHelper
{
  // Boilerplate code to register attached property "bool? DialogResult"
  public static bool? GetDialogResult(DependencyObject obj) { return (bool?)obj.GetValue(DialogResultProperty); }
  public static void SetDialogResult(DependencyObject obj, bool? value) { obj.SetValue(DialogResultProperty, value); }
  public static readonly DependencyProperty DialogResultProperty = DependencyProperty.RegisterAttached("DialogResult", typeof(bool?), typeof(ButtonHelper), new UIPropertyMetadata
  {
    PropertyChangedCallback = (obj, e) =>
    {
      // Implementation of DialogResult functionality
      Button button = obj as Button;
      if(button==null)
          throw new InvalidOperationException(
            "Can only use ButtonHelper.DialogResult on a Button control");
      button.Click += (sender, e2) =>
      {
        Window.GetWindow(button).DialogResult = GetDialogResult(button);
      };
    }
  });
}

This will allow you to write:

<Button Content="Click Me" my:ButtonHelper.DialogResult="True" />

and get behavior equivalent to WinForms (clicking on the button causes the dialog to close and return the specified result)