Question

I have a binding of the form:

Path=SpecialCollection[0]

The SpecialCollection class extends ObservableCollection and has an indexer property.

public T this[string propertyValue]
{
    get
    {
        // do stuff
        return default(T);
    }
}

My problem is that the binding attempts to get the indexer property value, instead of returning the 0th item in the collection. Is there a way to force the binding to treat 0 as an integer so it returns a collection element, instead of invoking the collection’s indexer property’s getter?

Answer 1

According to MSDN you can tell the binding the type of the value entered as index:

Inside indexers you can have multiple indexer parameters separated by commas (,). The type of each parameter can be specified with parentheses. For example, you can have Path=”[(sys:Int32)42,(sys:Int32)24]”, where sys is mapped to the System namespace.

I noticed that the Binding constructor taking a path string uses another PropertyPath constructor than the default PropertyPath type converter, said PropertyPath constructor does not work in this scenario. To avoid the problem avoid the Binding constructor by setting the Path property manually which invokes the conversion via type converter.

<!-- Does not work -->
<TextBlock Text="{Binding [(sys:Int32)0]}"/>
<!-- Does work -->
<TextBlock Text="{Binding Path=[(sys:Int32)0]}"/>