C# 自定义控件绑定不工作

我已经为ios创建了一个自定义的numbpad控件，现在尝试将它与MVVMCross绑定到我的ViewModel。但它不起作用。ViewModel中的值始终为null

号码牌的代码为：

    [Register("NumberPad")]
public partial class NumberPad : UIView
{

    public string Text {
        get;
        set;
    }


    public NumberPad(IntPtr h): base(h)
    {
        //SetUp ();         
    }

    public NumberPad (RectangleF frame) : base(frame)
    {
        SetUp ();

    }

    public NumberPad ()
    {           
        //SetUp ();         
    }

    void SetUp ()
    {
        var arr = NSBundle.MainBundle.LoadNib ("NumberPad", this, null);
        var v = Runtime.GetNSObject (arr.ValueAt (0)) as UIView;
        v.Frame = new RectangleF (0, 0, Frame.Width, Frame.Height);
        AddSubview (v);

        Number0.TouchUpInside += HandleTouchUpInside;
        Number1.TouchUpInside += HandleTouchUpInside;
        Number2.TouchUpInside += HandleTouchUpInside;
        Number3.TouchUpInside += HandleTouchUpInside;
        Number4.TouchUpInside += HandleTouchUpInside;
        Number5.TouchUpInside += HandleTouchUpInside;
        Number6.TouchUpInside += HandleTouchUpInside;
        Number7.TouchUpInside += HandleTouchUpInside;
        Number8.TouchUpInside += HandleTouchUpInside;
        Number9.TouchUpInside += HandleTouchUpInside;

    }

    void HandleTouchUpInside (object sender, EventArgs e)
    {
        int tag = ((UIButton)sender).Tag;

        if (tag >= 0 && tag <= 9) {
            Text = String.Format("{0}{1}",Text,tag);
        } else if (tag == 10 && Text.Length > 0) {
            Text = Text + Text.Substring (0, Text.Length - 1);
        }
    }
}

---

有什么想法吗？

如果希望MvvmCross自动获取属性中的更改，如：

public string Text {
    get;
    set;
}

然后您必须给MvvmCross一些方法来知道属性的值已经改变。最简单的方法是简单地提供一个具有常规名称的事件，并在文本更改时引发此更改，例如：

public event EventHandler TextChanged;

private string _text;
public string Text {
    get { return _text; }
    set {  _text = value; TextChanged.Raise(this);  }
}

有关自定义控件和自定义绑定的详细信息，请参见中的N=18、19、20和28

public event EventHandler TextChanged;

private string _text;
public string Text {
    get { return _text; }
    set {  _text = value; TextChanged.Raise(this);  }
}