XmlSerializer causes XamlParseException

Question

I have a simple WPF app and when I try to serialize a simple Exception with XmlSerializer, I get a XamlParseException.

The code in MainWindow.xaml is:

<Window x:Class="WpfApplication2.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Grid>

</Grid>
</Window>

The code in App.xaml is:

<Application x:Class="WpfApplication2.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         StartupUri="MainWindow.xaml">
<Application.Resources>

</Application.Resources>

The code of Serializer static class used for serialization is:

public static class Serializer<T>
{
    /// <summary>
    /// serialize an instance to xml
    /// </summary>
    /// <param name="instance"> instance to serialize </param>
    /// <returns> instance as xml string </returns>
    public static string Serialize(T instance)
    {
        StringBuilder sb = new StringBuilder();
        XmlWriterSettings settings = new XmlWriterSettings();

        using (XmlWriter writer = XmlWriter.Create(sb, settings))
        {
            XmlSerializer serializer = new XmlSerializer(instance.GetType());
            serializer.Serialize(writer, instance);
        }

        return sb.ToString();
    }

    /// <summary>
    /// deserialize an xml into an instance
    /// </summary>
    /// <param name="xml"> xml string </param>
    /// <returns> instance </returns>
    public static T Deserialize(string xml)
    {
        using (XmlReader reader = XmlReader.Create(new StringReader(xml)))
        {
            foreach (Type t in types)
            {
                XmlSerializer serializer = new XmlSerializer(t);
                if (serializer.CanDeserialize(reader))
                    return (T)serializer.Deserialize(reader);
            }
        }

        return default(T);
    }

    /// <summary>
    /// store all derived types of T:
    /// is used in deserialization
    /// </summary>
    private static Type[] types = AppDomain.CurrentDomain.GetAssemblies()
                                        .SelectMany(s => s.GetTypes())
                                        .Where(t => typeof(T).IsAssignableFrom(t)
                                            && t.IsClass
                                            && !t.IsGenericType)
                                            .ToArray();
}

The code in MainWindow.xaml.cs is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication2
{
  /// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        Exception e = new System.IO.IOException("blablabla", new System.IO.DirectoryNotFoundException());
        MessageBox.Show(Serializer<Exception>.Serialize(e));
    }
   }
  }

And when I run this, I get this exception:

'The invocation of the constructor on type 'WpfApplication2.MainWindow' that matches the specified binding constraints threw an exception.' Line number '3' and line position '9'.

What can be the problem?

Answer 1

What you would have seen if you had tested it out as an isolated problem was that the XmlSerializer throws an InvalidOperationException with the message

There was an error reflectig type 'System.IO.IOException'.

The inner exception holds a detailed description why:

Cannot serialize member System.Exception.Data of type System.Collections.IDictionary, ...

Dictionaries cannot be serialized with the .NET XML Serializer. That's that.