After applying update 2 VisualStudio 2015 Enterprise can't connect to TFS - exception TF205020

Question

VisualStudio 2015.1 Enterprise/TFS integration worked fine until VS2015 update 2 was applied.

Reinstalling/repairing VisualStudio didn't fix the issue, keep getting:

TF205020: Could not connect to server ...... The server returned the following error:

Could not load type Microsoft.VisualStudio.Services.WebApi.Utilities.UserAgentUtility' from assembly 'Microsoft.VisualStudio.Services.WebApi, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

SETUP:

VS Enterprise 2015.2 TFS 2015.2

Answer 1

We had the same issue here. Reinstalling Visual Studio 2015 after deleting cache, user profile folders and registry settings didn't help us. It looks like a TestComplete 11.31 installation installs some assemblies in the GAC which conflicts with Visual Studio 2015 Update 2. We fixed the issue comparing two almost identical systems (one with and one without TestComplete) and these assemblies we deleted from the %WINDOWS%\Microsoft.NET\assembly folder:

• Micorosft.VisualStudio.Services.Client
• Micorosft.VisualStudio.Services.Common
• Micorosft.VisualStudio.Services.Integration
• Micorosft.VisualStudio.Services.WebApi

But the problem still existed. After removing:

• Microsoft.TeamFoundation.Client
• Microsoft.TeamFoundation.WorkItemTracking.Common

the problem was gone!

I hope this will help your issue...

Answer 2

Thanks to Ernstjan Freriks, this additional info (originally from Microsoft Connect) helped me:

The Tfs client binaries should not be in your GAC. The only way they would get there is to add them yourself, or install some 3rd party application that has added them. Once they are in the GAC they will be loaded instead of the binary that matches your version of TeamExplorer or tf.exe. You need to remove all instances of any Team Foundation binary from the GAC including the following:

Microsoft.TeamFoundation.Build2.WebApi.dll
Microsoft.TeamFoundation.Chat.WebApi.dll
Microsoft.TeamFoundation.Common.dll
Microsoft.TeamFoundation.Core.WebApi.dll
Microsoft.TeamFoundation.Diff.dll
Microsoft.TeamFoundation.Discussion.Client.dll
Microsoft.TeamFoundation.Discussion.WebApi.dll
Microsoft.TeamFoundation.Git.Client.dll
Microsoft.TeamFoundation.Lab.Client.dll
Microsoft.TeamFoundation.Lab.Common.dll
Microsoft.TeamFoundation.Lab.TestIntegration.Client.dll
Microsoft.TeamFoundation.Lab.WorkflowIntegration.Client.dll
Microsoft.TeamFoundation.Policy.WebApi.dll
Microsoft.TeamFoundation.ProjectManagement.dll
Microsoft.TeamFoundation.SharePointReporting.Integration.dll
Microsoft.TeamFoundation.SourceControl.WebApi.dll
Microsoft.TeamFoundation.Test.WebApi.dll
Microsoft.TeamFoundation.TestImpact.Client.dll
Microsoft.TeamFoundation.TestManagement.Client.dll
Microsoft.TeamFoundation.TestManagement.Common.dll
Microsoft.TeamFoundation.TestManagement.WebApi.dll
Microsoft.TeamFoundation.VersionControl.Client.dll
Microsoft.TeamFoundation.VersionControl.Common.dll
Microsoft.TeamFoundation.VersionControl.Common.Integration.dll
Microsoft.TeamFoundation.Work.WebApi.dll
Microsoft.TeamFoundation.WorkItemTracking.Client.DataStoreLoader.dll
Microsoft.TeamFoundation.WorkItemTracking.Client.dll
Microsoft.TeamFoundation.WorkItemTracking.Client.QueryLanguage.dll
Microsoft.TeamFoundation.WorkItemTracking.Common.dll
Microsoft.TeamFoundation.WorkItemTracking.Proxy.dll
Microsoft.TeamFoundation.WorkItemTracking.WebApi.dll
Microsoft.VisualStudio.Services.Client.dll
Microsoft.VisualStudio.Services.Common.dll
Microsoft.VisualStudio.Services.WebApi.dll

You can use gacutil to remove these. Once removed your issue should be fixed.

Answer 3

To narrow down this issue:

1. Check Windows event viewer for more info of the errors.
2. Try to clear TFS and VS cache ,detail step with this blog
3. Try to make sure you can access the TFS web accesshttp://:8080/tfs/web/

Answer 4

The same as this issue: Extension fails to load on VS2015.2, try with the solution in it:

Can you check if Microsoft.VisualStudio.Services.WebApi.dll is installed into the GAC? The easiest way to do this is to check if there is a folder that starts with v14.0.0.0 under the c:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.VisualStudio.Services.WebApi.

I suspect you have an assembly from VS 2015 RTM or VS 2015 Update 1 in the GAC. Uninstalling it, will fix the issue.