Unable to load SOS in WinDbg

The CLR runtime dll was renamed to clr.dll with .NET 4. So in order to load the correct version of SOS you need to adjust your .loadby command. I.e. .loadby sos clr Also, if you’re on 64 bit, you should install the 32 bit version of Debugging Tools for Windows as well in order to … Read more

HtmlString vs. MvcHtmlString

HtmlString only exists in ASP.NET 4. MvcHtmlString was a compatibility shim added to MVC 2 to support both .NET 3.5 and .NET 4. Now that MVC 3 is .NET 4 only, it’s a fairly trivial subclass of HtmlString presumably for MVC 2->3 for source compatibility. If you’re ever going to drop back to MVC 2 … Read more


ASP.NET 4 was not registered in IIS. Had to run the following command in the command line/run 32bit (x86) Windows %windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -ir 64bit (x64) Windows %windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -ir Note from David Murdoch’s comment: That the .net version has changed since this Answer was posted. Check which version of the framework is in the %windir%\Microsoft.NET\Framework64 directory and … Read more