WPF DataBinding where the Path is recovered from the object? - wpf

Question

I have an object with several properties. Two of these are used to control the width and height of the target text box. Here is a simple example...
<DataTemplate DataType="{x:Type proj:SourceObject}">
<TextBox Width="{Binding ObjWidth}" Height="{Binding ObjHeight}"/>
</DataTemplate>
I also want to bind the Text property of the TextBox. The actual property to bind against is not fixed but instead is named in a field of the SourceObject. So ideally I would want to do this...
<DataTemplate DataType="{x:Type proj:SourceObject}">
<TextBox Width="{Binding ObjWidth}" Height="{Binding ObjHeight}"
Text="{Binding Path={Binding ObjPath}"/>
</DataTemplate>
Here the ObjPath is a string that returns a path that would be perfectly valid for the binding. But this does not work because you cannot use a binding against the Binding.Path. Any ideas how I can achieve the same thing?
For more context I will point out that the SourceObject is user customizable and hence the ObjPath can be updated over time and hence I cannot simply put a fixed path in the data template.

Answer 1

You could implement an IMultiValueConverter and use this one as BindingConverter for your Text Property. But then you have the problem, that the value of the Textbox is only updated if your ObjPath property changes (the path itself), not the value where the path is pointing to. If that's, okay you can go with a BindingConverter which returns the value of your binding Path using Reflection.
class BindingPathToValue : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value[0] is string && value[1] != null)
{
// value[0] is the path
// value[1] is SourceObject
// you can use reflection to get the value and return it
return value[1].GetType().GetProperty(value.ToString()).GetValue(value[1], null).ToString();
}
return null;
}
public object[] ConvertBack(object value, Type[], object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
Have the converter in your Resources:
<proj:BindingPathToValue x:Key="BindingPathToValue" />
and use it in XAML:
<DataTemplate DataType="{x:Type proj:SourceObject}">
<TextBox Width="{Binding ObjWidth}" Height="{Binding ObjHeight}">
<TextBox.Text>
<MultiBinding Mode="OneWay" Converter="{StaticResource BindingPathToValue}">
<Binding Mode="OneWay" Path="ObjPath" />
<Binding Mode="OneWay" Path="." />
</MultiBinding>
</TextBox.Text>
</TextBox>
</DataTemplate>