Magnus Lindhe

Using ReactiveUI to bind to controls that do not support data binding

I am using ReactiveUI in Windows Forms project and want to bind a view model property to a tool strip menu item checked property. The ToolStripMenuItem control is not bindable and there is no built in support for this control in ReactiveUI.

A simple two way bind will not work since the control will not notify about property changes:

this.Bind(ViewModel, vm => vm.ReuseAddresses, view => view.ReuseAddresses.Checked);

ReactiveUI to the rescue! There is an overload method that will allow you to pass an observable (of any type) that will trigger an update of the view model property:

this.Bind(ViewModel, vm => vm.ReuseAddresses, view => view.ReuseAddresses.Checked, ReuseAddresses.CheckedObservable());

I made a simple extension method on ToolStripMenuItem that returns an observable for the CheckedChanged event like this:

public static IObservable<bool>  CheckedObservable(this ToolStripMenuItem self)
    var observable = Observable
            h => self.CheckedChanged += h,
            h => self.CheckedChanged -= h
        .Select(e => ((ToolStripMenuItem)e.Sender).Checked);

    return observable;

There is a NuGet package ReactiveUI.Events that adds lots of extension methods for events in WPF. But for Windows Forms you are stuck with creating your own, at least for now.

comments powered by Disqus