“Unable to launch the IIS Express Web server.” in Visual Studio

Question

I attempted to run my web service through visual studio. I faced an issue like :

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Microsoft Visual Studio
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Answer 1

I had this problem when upgrading an MVC project. I copied over the newer-MVC .csproj over my existing .csproj file then worked back to a fully working Project. What I failed to consider is the existing port number in the old .csproj. The new project had a new port number, yet shared the Project/Assembly Name. That was enough to make IIS Express lose its mind and throw this exception.

Just digging the old port number out of git and changing the IIS Express URL to include it in Project Settings was enough to fix it.