Can you provide an example of creating a custom TargetBinding in MVVMCross

Step 1: Define the Custom Target Binding Class

First, you need to create a class that inherits from `MvxPropertyInfoTargetBinding` or another appropriate base class depending on your needs. For a simple property binding, `MvxPropertyInfoTargetBinding` is suitable.

csharp
public class MyViewMyPropertyTargetBinding : MvxPropertyInfoTargetBinding
{
    private bool _subscribed;

    public override MvxBindingMode DefaultMode => MvxBindingMode.TwoWay;

    public MyViewMyPropertyTargetBinding(object target, PropertyInfo targetPropertyInfo)
        : base(target, targetPropertyInfo)
    {
    }

    protected override void SetValueImpl(object target, object value)
    {
        var view = target as MyView;
        if (view == null) return;
        view.MyProperty = (string)value;
    }

    public override void SubscribeToEvents()
    {
        var myView = View;
        if (myView == null)
        {
            MvxBindingTrace.Trace(MvxTraceLevel.Error, "Error - MyView is null in MyViewMyPropertyTargetBinding");
            return;
        }

        _subscribed = true;
        myView.MyPropertyChanged += HandleMyPropertyChanged;
    }

    private void HandleMyPropertyChanged(object sender, EventArgs e)
    {
        var myView = View;
        if (myView == null) return;
        FireValueChanged(myView.MyProperty);
    }

    protected override void Dispose(bool isDisposing)
    {
        base.Dispose(isDisposing);
        if (isDisposing)
        {
            var myView = View;
            if (myView != null && _subscribed)
            {
                myView.MyPropertyChanged -= HandleMyPropertyChanged;
                _subscribed = false;
            }
        }
    }
}

Step 2: Register the Custom Target Binding

After defining the custom `TargetBinding`, you need to register it in your `Setup.cs` file. This is done by overriding the `FillTargetFactories` method:

csharp
protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry)
{
    base.FillTargetFactories(registry);
    registry.RegisterPropertyInfoBindingFactory(
        typeof(MyViewMyPropertyTargetBinding),
        typeof(MyView), "MyProperty");
}

Step 3: Use the Custom Target Binding in Your View

Now that the custom binding is registered, you can use it in your views like any other binding:

csharp
MyView aView;
set.Bind(aView).For("MyProperty").To(vm => vm.value);

Explanation

- TargetBinding Class: The `MyViewMyPropertyTargetBinding` class defines how to bind `MyProperty` of `MyView`. It handles setting the property value and subscribing to the `MyPropertyChanged` event for two-way binding.
- Registration: The binding is registered in `Setup.cs` to make it available for use.
- Usage: The custom binding is used in views by specifying the property name (`MyProperty`) and the source property (`vm.value`) in the view model.

This example demonstrates how to create a custom `TargetBinding` for a specific property, enabling two-way data binding in MvvmCross.