If you are getting Microsoft.WITDataStore32.dll issue while dealing with TFS/ VSTS ie. getting project name or fetching test case id in Visual Studio 2015 then you can simply redirect the Team Foundation dlls to version 12.0.0.0 from 14.0.0.0 as 14 version dlls create issue while retrieving such data and we use to get such error.
I have faced issue "Unable to load DLL 'Microsoft.WITDataStore32.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)" while running my Coded UI test script after migration from "TFS 2012 and VS2013" to "VSTS and VS2015" respectively.
The issue got resolved when i redirected the referenced 14 versions dll to 12 version in the App config as shown below:
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="Microsoft.TeamFoundation.Common" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
<bindingRedirect oldVersion="14.0.0.0" newVersion="12.0.0.0"/>
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Microsoft.TeamFoundation.TestManagement.Client" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
<bindingRedirect oldVersion="14.0.0.0" newVersion="12.0.0.0"/>
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Microsoft.TeamFoundation.WorkItemTracking.Client" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
<bindingRedirect oldVersion="14.0.0.0" newVersion="12.0.0.0"/>
</dependentAssembly>
</assemblyBinding>
Regards,
Prasidh