Adding MVC4 to a project: The operation could not be completed. Not implemented

While experimenting around with adding the MVC framework onto an existing C# Webforms project, I came across an interesting error when trying to add the MVC3/MVC4 project type GUID into the existing csproj file for the project (I tried both, seeing if there was something wrong with that). I came up with the following error when first opening the solution with the project (this was using Visual Studio 2012):

“The operation could not be completed. Not implemented”

That was very…descriptive. I went ahead and repaired the MVC4 package thinking that might fix it, but it was no good. Made sure Visual Studio was up to date – it was. I was pretty stumped. I took another look at the csproj file. Before adding MVC4 to the project, I had the following:

{349c5851-65df-11da-9384-00065b846f21};
{fae04ec0-301f-11d3-bf4b-00c04f79efbc}

So it’s your basic web application project {349c5851-65df-11da-9384-00065b846f21} combined with a C# project {fae04ec0-301f-11d3-bf4b-00c04f79efbc}. So, I went ahead and added in the MVC4 type {E53F8FEA-EAE0-44A6-8774-FFD645390401} to get the following code:

{349c5851-65df-11da-9384-00065b846f21};
{fae04ec0-301f-11d3-bf4b-00c04f79efbc};
{E53F8FEA-EAE0-44A6-8774-FFD645390401}

Seems like it should work. I compared the above to a newly created MVC project and apparently, the problem exists with the order that the project type GUIDs are listed in. I had added the MVC4 project type GUID after everything, whereas it needs to go before the others, like so:

{E53F8FEA-EAE0-44A6-8774-FFD645390401};
{349c5851-65df-11da-9384-00065b846f21};
{fae04ec0-301f-11d3-bf4b-00c04f79efbc}

Problem is, I can’t seem to find any sort of documentation for this behavior. It really shouldn’t matter what order the project type GUIDs are in, right? I can understand from a developer standpoint that MVC depends on the Web application framework which depends on the C# project – and in that way, the project can correctly identify the build order – but I thought that this was something that Visual Studio would have been able to figure out more easily (without having to list the project type GUIDs in the proper order). Anyways, after figuring that out, MVC worked with the existing Webforms application like a champ.