Cant start Toolbox. "Unexpected error ..."

Topics: Bug
Jan 22, 2015 at 10:19 AM
Edited Jan 22, 2015 at 11:09 AM
I am using Windows 7 SP1 and have .Net Framework 3.5, IIS and Windows Identity Foundation installed.

I download the file, unlock it, unzip it, and try to run XrmToolBox.exe and I get a nasty error:
"An unexpected error has ocurred: System.TypeLoadException: Could not load type 'System.Runtime.CompilerServices.ExtensionAttribute' from assembly 'mscorlib, Version ..."
At the bottom of the screen it says
"One reason can be that at least one file is locked by Windows. Please unlock each locked file or unlock before extracting its content."
I checked and sure enough, was locked. So I erased everything I had unzipped, unlocked it (right-click, Properties, unlock) and unzipped it again. And I still get this error. I also check each individual file in the zip, none are locked.

I have no idea what the problem might be. I am not a .NET or Dynamics developer, I am just trying to install this app (which everyone in the Dynamics world raves about) to see what the SOAP requests and responses look like, so I can create a Java client that connects to Dynamics/ADFS.

Any help much appreciated.
Jan 22, 2015 at 1:59 PM
If you downloaded the latest version, it also requires the latest version of the .net Framework ( It should prompt you and tell you that the newest version of .net is required, so that may not be your issue, but you will need to have it.
Marked as answer by syg6 on 1/22/2015 at 8:48 AM
Jan 22, 2015 at 3:47 PM
Right you are. I had .NET Framework 3.5 and some other thing that was .NET Framework 4, but apparently not the whole framework ...

I really don't know, I've never used .NET before. At any rate, after installing 4.5.2 it works.

Many thanks, I had no idea what the problem was.