Question: I have generated my xml coverage file as part of CI build on the TFS server using vNext 2015 build definition. How would one display the results in the TFS 2015 summary ? Either using the xml report or the html generated using the ReportGenerator.

Answer: 
You need to convert the results produced by OpenCover to a format which can be parsed by TFS.

One way to do this would be to use the [OpenCoverToCoberturaConverter](https://github.com/danielpalme/OpenCoverToCoberturaConverter) NuGet package.

Once you have that, you can use the *Publish Code Coverage Results* build step.

I have described the whole process on [my blog](http://codewithstyle.info/setting-up-coverage-reports-on-vsts-with-opencover/).
In “TFS 2015 - Update 2” this is possible by writing your own vsts extension (see here: <https://www.visualstudio.com/en-us/docs/integrate/extensions/overview> ).

I set up my own 'learning project' for building this as .vsix here: <https://github.com/RobertK66/vsts-opencover>.

My custom build step uses nunit3 console runner to execute tests under opencover.
I managed to upload the OpenCover xml result file as 'testrun-attachment' via REST-interface and got the pieces in place to show the summary values on both the build summary tab and on its own extended “build-results-view”.

Base for this first version were a lot of examples provided by MS on github: <https://github.com/Microsoft/vsts-tasks> and <https://github.com/Microsoft/vsts-extension-samples>

To get a first feeling what places on your TFS Web Portal can be extended/customized you can download and install this extension <https://aha.gallery.vsassets.io/items?itemName=ms-samples.samples-contributions-guide> from the Visual Studio Marketplace.

Hope this helps to get you started.