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Xamarin obj\Debug\libraryimports.cache does not exist

I am new at Xamarin.Android with Visual Studio 2015 and tried to create a little test application.
As soon as I create the new project, a warning appears:
obj\Debug\libraryimports.cache does not exist. No Imported Libraries found.
If I try to start the application, VS tells me, that there is a problem and asks me to go further.
I tried to reinstall Xamarin and Visual Studio and tried to create the Project on my Desktop.
In every case it shows me the same Warning.
Can anybody help me?

For me it helped to move the whole Visual Studio solution to a path with only ASCII characters.

Move the solution to c:\new_folder\solution. new_folder and solution must contains only ASCII characters. My username in windows has "í".
This solution work for me.

Looks like reinstalling is the only known solution: Rebuild failed: ''obj\Debug\libraryimports.cache does not exist. No Imported Libraries found''

Visual Studio throws errors when attaching to Unity

All of a sudden when I try to attach to Unity 5.2 with Visual Studio 2015 I get a bunch of errors as seen in screenshot below. This is the second this has happened this week. Last time I had to create a new project and bring everything over to resolve the issue. Unity plays fine, no errors...but visual studio throws errors when I try to attach. It worked earlier this evening.

Few things to consider when project shows error while being fully functional in Unity3D Editor itself:
Can you build your project in Visual Studio even if errors are shown? If so, there is possiblity that these are just leftovers from Unity3D building your project - should disappear on first successful build from VS
If you can't build your project, have you tried to remove your Library folder from project's root folder? In many cases it will fix the problem but will end up in forcing Unity3D to rebuild some of the files it had previously in Library folder.
Have you added any new libraries (dll's) to project? Any chance they might be installed/added in a wrong way? If so, try readding them to project (if it's a classic dll) or readd plugin that you have troubles with.
I would leave version incompability as it would end up with errors in Unity3D console. Same with errors with solution per se.

When I changed target framework to Unity 3.5 .net full Base Class Libraries the build errors went away.
I found the solution posted by Nathan Koop here: Type or namespace name does not exist

Visual Studio 2010 Pro: Error when creating project

For whatever reason this error comes up when making a project, even though this is an error I expect to see at runtime or when there is a null variable. All that visual studio creates in the project solution is a reference folder.
I've installed Visual Studio 2010 Pro from an Image file on a disk and I've reinstalled/repaired both VS and the Service Pack 1.
Is this just a known error? Should I be concerned about running the program correctly? It is especially important that I have all the libraries/content folders since I'm going to be using XNA to develop an Xbox game.
Sorry can't post pictures yet.
A problem was encountered creating the subproject "WindowsGame1". Object reference not set to an instance of an object.

Found the error, which is somewhat along the lines of reinstall/repair.
Basically, I have windows phone sdk installed and I repaired it, somehow fixing my xbox/windows games.
Thanks for leading me to other solutions though, if anyone still has this problem I'd recommend reinstalling/repairing visual studio, sdk, frameworks 4.5, etc. the problem is bound to be an installation error.
Plus, I had to uninstall old 2008 or stand-alone visual c#, c++ IDEs.

Missing project sub type error when trying to create a new MonoGame project

Hello Im using Visual Studio 2012 and whenver I try to create a new MonoGame content project I get this error...Also if I try to start a windows Mono project or a Android mono project I dont get the same error but whenever i try to compile i get errors, i have unstillaed Mono and xamarin and tried installing and that never solved the issue the only thing left to do is uninstall Visual Studio 2012 but that can take a ton of time so if anyone here can help me it will be appreciated here is the link to the following error.

I think I have a workaround for you, although, I still don't fully understand the issue myself and I'd love someone to shed some light on it.
If you open up the project file as plain text you will see a ProjectTypeGuids like so:
<ProjectTypeGuids>{9B831FEF-F496-498F-9FE8-180DA5CB4258};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
If you Google each GUID you will find that one of them is DotNetProjectSubtype id="MonoGame" and the other is Windows (C#).
As far as I can tell you can safely delete the MonoGame one and proceed with your day. I believe it's only used at project creation time.

Unable to set TestContext property

I have a visual studio 2008 Unit test and I'm getting the following runtime error:
Unable to set TestContext property for the class JMPS.PlannerSuite.DataServices.MyUnitTest. Error: System.ArgumentException: Object of type 'Microsoft.VisualStudio.TestTools.TestTypes.Unit.UnitTestAdapterContext' cannot be converted to type 'Microsoft.VisualStudio.TestTools.UnitTesting.TestContext'
I have read that VS 2008 does not properly update the references to the UnitTestFramework when converting 2005 projects. My unit test was created in 2008 but it inherits from a base class built in VS 2005. Is this where my problem is coming from? Does my base class have to be rebuilt in 2008? I would rather not do this as it will affect other projects.
In other derived unit tests built in 2005, all that we needed to do was comment out the TestContext property in the derived unit test. I have tried this in the VS 2008 unit test with no luck. I have also tried to "new" the TestContext property which gives me a different runtime error.
Any ideas?

I had the same problem in Visual Studio 2012 when I upgraded an older project (i think 2005).
The Reference to Microsoft.VisualStudio.QualityTools.UnitTestFramework needs to be removed by right clicking it in the Solution Explorer then removing it.
To add the right one:
Add New Reference
Extensions, find Microsoft.VisualStudio.QualityTools.UnitTestFramework, there are likely several
Mouse over to display the path, choose the one in ../IDE/PublicAssemblies
Clean
Rebuild
Rerun tests

I'm posting this here in the hopes that it helps someone unit testing a smart device project. I got a very similar error when I first tried to run a unit test for a method in a smart device project I was working on in Visual Studio 2008:
Error: System.ArgumentException: Object of type 'Microsoft.VisualStudio.TestTools.TestTypes.Unit.UnitTestAdapterContext' cannot be converted to type 'Microsoft.VisualStudio.TestTools.UnitTesting.TestContext'
Googling the error returned results that suggested it was caused by upgrading a test project from Visual Studio 2005 format to 2008, and that the reference to the UnitTestFramework.dll was still for the old version (8.0) and required updating. This did not apply to me as I had not upgraded my test project from VS2005. So I continued searching.
After hours of searching for other causes for the error without success, I stumbled upon the following references in the smart device project:
Microsoft.WindowsMobile.dll
Microsoft.WindowsMobile.Status.dll
Visual Studio was obtaining these references from the following folder:
C:\Program Files\Windows Mobile 5.0 SDK R2\Managed Libraries
However, the smart device project's target platform was the Windows Mobile 6 Professional SDK. I didn't notice this before as I did not originally create the smart device project. So I removed the references to the two DLLs and readded them from the following folder:
C:\Program Files\Windows Mobile 6 SDK\Managed Libraries
After rebuilding the smart device project, running the test method succeeded.

I ran into the same issue. Turned out that one of my projects was referencing the 8.0 assemblies and the other was referencing 9.0. The solution compiled, but I got a runtime exception.