Instructions for configuring the VS IDE for WinMerge are available on the Paul Bouwer user blog Replace the diff / merge tool in Visual Studio Team System with WinMerge :
In Visual Studio, under Tools> Options> Source Control> Visual Studio Team Foundation> Customize Custom Tools, add entries to compare and merge using the specified options.
Works great in the VS IDE if the Compare command is available, for example, in the Pending Changes and Changes window.
Also works great with integration with Windows Explorer and as a standalone tool.
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