Attila Horváth Attila Horváth - 4 months ago 65
C# Question

Invalid Resx file. Could not load type error why?

I'm getting designer error on code:

The Component i'm willing to define a List of properties for:

using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;

namespace TestProjectForProperty.Test
public class MyTreeView : TreeView
private List<TypeDescriptorBase> _descriptorsAvailable = new List<TypeDescriptorBase>();

public List<TypeDescriptorBase> DescriptorsAvailable
get { return _descriptorsAvailable; }
set { _descriptorsAvailable = value; }

The Descriptor itself:

using System;

namespace TestProjectForProperty.Test
public class TypeDescriptorBase
public string Name { get; set; }

public override string ToString()
return Name;

I am getting the following error if i try to use the component for example on a form and add any items on the property sheet or in the component's constructor to the DescriptorsAvailable property

Error 1 Invalid Resx file. Could not load type
TestProjectForProperty, Version=, Culture=neutral,
PublicKeyToken=null]], mscorlib, Version=, Culture=neutral,
PublicKeyToken=b77a5c561934e089 which is used in the .RESX file.
Ensure that the necessary references have been added to your project.
Line 134, position 5. ...\visual studio
2010\Projects\TestProjectForProperty\TestProjectForProperty\Form1.resx 134 5 TestProjectForProperty

In the Resx file there is data field with base64 encoded stuff inside when this error is present.

I have been searching for an answer, but the best i got is to restart everything, it didn't help me, do you guys have any suggestions? I'm using .net 4 client and visual studio 2010


Put the MyTreeView and TypeDescriptorBase classes into another project and reference it from your GUI project will resolve the issues.

I'm not sure why exactly the problem occurs - I guess it has something to do with the way the serializing process is generating the base64 string for the DescriptorsAvailable Property. Maybe somebody else can give us some insight.