Question

How do i extend an existing control (ComboBox in my case) to include a new property which i can bind to a property on my view model??

I have a Dependancy Property on the control’s class as follows:

public class MyComboBox : ComboBox
{
    public static readonly DependencyProperty MyTextProperty =
        DependencyProperty.Register("MyText", typeof(string), typeof(MyComboBox));

    public string MyText
    {
        get
        {
            return GetValue(MyComboBox.MyTextProperty).ToString();
        }

        set
        {
            SetValue(MyComboBox.MyTextProperty, value);             
        }
    }

And want to bind to it declaratively from XAML like this:

<MyComboBox MyText="{Binding MyTextOnViewModel,
    UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>  

The Binding just won’t work, any ideas why??

Thanks.

Answer 1

Your getter and setter reference TestTextProperty while the property is declared as MyTextProperty.

Your getter should also be casting instead of calling .ToString()

return (string)GetValue(MyTextProperty);

See this page for more complete instructions.