KeyNotFoundException: The given key was not present in the dictionary.
System.Collections.Generic.Dictionary2[System.String,UnityEditor.VisualStudioIntegration.ScriptingLanguage].get_Item (System.String key) (at /Applications/buildAgent/work/b59ae78cff80e584/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:151) UnityEditor.VisualStudioIntegration.SolutionSynchronizer.ProjectFile (MonoIsland island, Boolean forVisualStudio) (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:293) UnityEditor.VisualStudioIntegration.SolutionSynchronizer+<GetProjectEntries>c__AnonStorey51.<>m__B9 (MonoIsland i) (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:351) System.Linq.Enumerable+<CreateSelectIterator>c__Iterator102[UnityEditor.Scripting.MonoIsland,System.String].MoveNext ()
System.Collections.Generic.List1[System.String].AddEnumerable (IEnumerable1 enumerable) (at /Applications/buildAgent/work/b59ae78cff80e584/mcs/class/corlib/System.Collections.Generic/List.cs:128)
System.Collections.Generic.List1[System.String]..ctor (IEnumerable1 collection) (at /Applications/buildAgent/work/b59ae78cff80e584/mcs/class/corlib/System.Collections.Generic/List.cs:65)
System.Linq.Enumerable.ToArray[String] (IEnumerable1 source) UnityEditor.VisualStudioIntegration.SolutionSynchronizer.GetProjectEntries (IEnumerable1 islands, Boolean forVisualStudio) (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:356)
UnityEditor.VisualStudioIntegration.SolutionSynchronizer.SolutionText (IEnumerable1 islands, Boolean onlyCSharp) (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:340) UnityEditor.VisualStudioIntegration.SolutionSynchronizer.SyncSolution (IEnumerable1 islands) (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:331)
UnityEditor.VisualStudioIntegration.SolutionSynchronizer.Sync () (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:172)
UnityEditor.SyncVS.SyncVisualStudioProjectIfItAlreadyExists () (at C:/BuildAgent/work/7535de4ca26c26ac/Editor/Mono/SyncProject.cs:115)
Can you try and re-attach your image as it does not seem to be appearing. Could you also be a little more specific about the error and your project as I explained on facebook, it would make it much easier to diagnose.
It’s a bit tricky to tell exactly what is going on here. It would appear at first glance as if there are some file extension in use that causes the issue, but the log looks a bit deeper than that so, yeah, it’s hard to tell.
Have you ever been able to open the solutions in the past or did this start happening at some point into your project?
I think it would be easier for us to work through the support system. I invite you to submit a bug report with your project, send an email to support@unity3d.com with a link to this thread, your bug number, a complete editor log and let us know when/how this problem started appearing.
Also what version of Unity are you using?
latest one, i got this problem when i was building and running to try out my game.
Pro Tip: Answer the questions of people who try to help you!