Does Team Foundation Service have a built in Wiki like GitHub does?
If not is there one that can be easily integrated?
No it does not, you could try using CodePlex instead. This has the option to store your source code using TFVC and use Team Foundation features such as work items and queries, but also allows you to have "documentation", which is in a wiki style.
Team Foundation Service is Cloud Hosted TF. CodePlex is Microsoft's open source platform.
Brian Harry as also stated there are plans to align CodePlex and TF Service most closely.
And, as I alluded to earlier, we’ll be working to align CodePlex and Team Foundation Service into a single, scalable offering.
Visual Studio Team Services now includes a wiki, though it's currently in preview mode. To enable it, select "Preview Features" in the profile menu and set the wiki to on.
Detailed instructions are at https://www.visualstudio.com/en-us/docs/collaborate/add-edit-wiki
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With