Invalid Resx file. Could not load type error why?

Question

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>();

        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        public List<TypeDescriptorBase> DescriptorsAvailable
        {
            get { return _descriptorsAvailable; }
            set { _descriptorsAvailable = value; }
        }
    }
}

The Descriptor itself:

using System;

namespace TestProjectForProperty.Test
{
    [Serializable]
    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 System.Collections.Generic.List`1[[TestProjectForProperty.Test.TypeDescriptorBase, TestProjectForProperty, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]], mscorlib, Version=4.0.0.0, 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

Answer 1

In my experience, this is due to a change of version of a referenced library, or a change of the lib itself, which contains the backing type of a property you have defined in your user control. The solution is to "force" the visual studio designer to re-initialize it's designer code for that type, and not expect to retrieve a "canned" version of it from the .resx file of the control.

1) Delete the offending data section in the .resx file of your control. This will be a section in the xml of the .resx file associated with your user control, which has a node: <data></data> - the name attribute will be set to whatever you've named that object in the properties of whatever you added this type to. The <data>/data> section contains a base64 encoded string that is the encoded form of the name and version of the library the type comes from. This is where the problem ism, because it now contains an encoded version of the library and/or version number you are no longer referencing in order to include the type. Delete the entire <data>/data> section, from opening to closing tag, save the change and close the file. Now the "artifact" is gone.

2) Now find the place in the designer file for your control, where the type is instantiated; this is initialization code generated for you by visual studio, and it is the place that is expecting to load a "canned" definition of the type from the base64 encoded string contained within the .resx file. The line will look something like this:

this.myCtrlFoo.MyPropertyFroo = ((MyNamespaceFoo.MyTypeFoo)(resources.GetObject("myCtrlFoo.MyPropertyFroo")));

...now just replace the resources.GetObjec call with the instantiation of a new instance of the appropriate type like so:

this.myCtrlFoo.MyPropertyFroo = ((MyNamespaceFoo.MyTypeFoo)(new MyNamespaceFoo.MyTypeFoo()));

...now save the change to the file, close it, rebuild, and everything should now build & run OK.