Question

I’m using a value converter which needs to get a list of types, which is a property of the converter. If I would use list of double values, I could use the following syntax (which is working as expected):

Code

public class MyConverter : IValueConverter
{
    public List<double> MyList { get; set; }

    // ...
}

XAML

<Converter:MyConverter x:Key="MyConverter">
    <Converter:MyConverter.MyList>
        <System.Double>1</System.Double>
        <System.Double>2</System.Double>
    </Converter:MyConverter.MyList>
</Converter:MyConverter>

But if I try to use this approach with a list of types, an exception is thrown:

Object of type 'System.RuntimeType' cannot be converted to type 'System.Collections.Generic.List`1[System.Type]'

This is my converter and its usage:

Code

public class MyConverter : IValueConverter
{
    public List<Type> MyList { get; set; }

    // ...
}

XAML

<Converter:MyConverter x:Key="MyConverter">
    <Converter:MyConverter.MyList>
        <x:Type TypeName="MyType1" />
        <x:Type TypeName="MyType2" />
    </Converter:MyConverter.MyList>
</Converter:MyConverter>

I guess the XAML syntax is wrong but I can’t find the right syntax.

Answer 1

Seems like bug in the XAML designer. The given bellow code worked for me. I can build and run application. But In the designer R# hightlights two lines with System:Type and the designer crashes with next two errors per line:

Error 1 Type ‘Type’ is not usable as an object element because it is
not public or does not define a public parameterless constructor or a
type converter.
Error 2 The type ‘Type’ does not support direct
content.
So when I’ve tried that solution before (before giving previous solution) I thought I am doing smth wrong.
But compiler still doesn’t give any error on build. Anyway here how it looks:

<Window.Resources>
    <local:Holder x:Key="one">
        <local:Holder.Types>
            <System:Type>System:Int32</System:Type>
            <System:Type>System:Double</System:Type>
        </local:Holder.Types>
    </local:Holder>
</Window.Resources>
<Grid >
    <ListBox DataContext="{StaticResource one}" ItemsSource="{Binding Path=Types, Converter={StaticResource one}}" />
</Grid>

As far as you can see, the difference is in the declaration. You have to use System.Type rather than x:Type.

and the code as a sample

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Windows.Data;
using System.Linq;

namespace stackProjects
{
    public class Holder : IValueConverter
    {
        public List<Type> Types { get; set; }

        public Holder()
        {
            Types=new List<Type>();
        }

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return Types.Select(x => x.Name).ToList();
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

As I was said, this happens because Type class is abstract.
Hope it helps