My edited files not appear in TFS's Pending Changes window

Go to File -> Source Control -> Go Online and it will fix this problem.

I didn't see File -> Source Control -> Go Online option. I fixed it by clicking on item and selecting option to check out for edit. That worked.

Did you already opened the project that you are working on through the Source control window? If you do that and your solution is not yet bound to TFS it will be asked now. So bind your solution and projects and then your changes will be visible and you do not need to do check out to edit. You can also see if this is already done by checking if there are vssscc files next to your solution files.