Project could not be opened because the Microsoft Visual C# 2010 compiler could not be created. An item with the same key....
I got this error after opening an existing VS2015 project after upgrading to Windows 10. I had definitely used this successfully before the upgrade and as usual, it's a very unhelpful message.
All the projects loaded apart from one and clicking "reload project" made the error display.
The issue is that User Account Control, which was previously disabled in Windows 7 was re-enabled. This meant that Visual Studio was not being opened as Administrator and rather than having a useful error, it shows this instead. I looked in the window at the bottom and something else was displayed about IIS that was more specific to the access permission problem.
I need to disable UAC again since giving permission every time you open VS is a pain!
All the projects loaded apart from one and clicking "reload project" made the error display.
The issue is that User Account Control, which was previously disabled in Windows 7 was re-enabled. This meant that Visual Studio was not being opened as Administrator and rather than having a useful error, it shows this instead. I looked in the window at the bottom and something else was displayed about IIS that was more specific to the access permission problem.
I need to disable UAC again since giving permission every time you open VS is a pain!