多加挖掘，原来我真的想把它绑定到一个ContentControl"标签上，如下:

Doing more digging, it turns out that I really wanted to bind this to a "ContentControl" tag, as follows:

XAML:

<ContentControl Content="{Binding WindowsControl}"/>

视图模型:

    private System.Windows.Forms.Control _myControl;

    public WindowsFormsHost STKObject
    {
        get 
        {
            return new WindowsFormsHost() { Child = _myControl};
        }
    }