.net - Could not find type 'xxx.xxx.xxx'. Please make sure that the assembly

Question

I've searched StackOverflow and found similar problems when I try and open a form that references a UserControl in a different project.

I get the

To prevent possible data loss before loading the designer, the following errors must be resolved:

message relating to the following two errors:

Could not find type 'MyNamespace.CommonUi.InformationBox'. Please make sure that the assembly that contains this type is referenced. If this type is a part of your development project, make sure that the project has been successfully built using settings for your current platform or Any CPU.

AND

The variable 'InformationBox1' is either undeclared or was never assigned.

InformationBox1 is an instance of the user control InformationBox that is on the form in the designer - it's just referenced as;

Friend WithEvents InformationBox1 As MyNamespace.CommonUi.InformationBox

The MyNamespace.CommonUi project builds successfully.

I get intellisense in the project so I'm reasonably confident that it's being referenced correctly.

So far, the same as other people have had:

This is a project that's been migrated from .NET2/x86 in VS2005 to .NET4/x64 in VS2012.

Now when the solution is running under 64 bit it doesn't work and I get this designer error. However, if I switch it to 32 bit (well technically AnyCPU) I can open the designer just fine.

I've read through the other suggestions in similar threads but they don't see to provide any solution (I've even gone as far as the "move it left & right to get it to rebuild" option)

Answer 1

I believe the issue is that Visual Studio is natively 32bit and one cannot do GUI editing for some components (E.g. ListView) in 64bit. E.g. on forms where you have ListView, you need to change the solution to 32bit to edit the GUI.

So the answer in short is, when you're facing this issue:

1. Change the solution to 32bit or AnyCPU
2. Clean and rebuild the solution/project
3. Open the GUI for editing
4. Save, change the solution back to 64bit
5. Clean and rebuild
6. Run in 64bit

Unfortunately Visual Studio doesn't come in 64bit as yet, hence all controls need to be designed in 32bit mode (or AnyCPU mode).

See this question for more details.

VS 2010 designer error 'Could not find type XYZ' in Windows7. Works fine in XP