As pointed out in this SO answer, the Add > Existing item dialog in Visual Studio by default displays the Add button (meaning that the selected items will be physically copied to the new location), whereas the desirable action is often (always?) to Add as Link.
Is it possible to configure Visual Studio so that Add as link is selected by default when opening the Add > Existing item dialog?
I have thoroughly searched the Options dialog in Visual Studio and examined the MSDN documentation for an answer to this, but so far to no avail.
Project Linker would be a good option for automated linking when two new projects are to share the same code base. However, when linking a large number of files from an existing to a new project, one seems to be confined to the Add > Existing item approach, and this work could be much more convenient and less prone to error if Add as link would be the default action.
Unfortunately, there is no option for that. But there is silver lining. You can drag files to a project and drop them to desired folder. Files are copied to your project. If you press Alt key doing drag and drop operation, files are not copied but linked instead.
You can also use VSCommands extension which adds 'Copy as Link' on folders and files in Solution Explorer. After that you can do 'Paste Link' in desired location. It also allows you to navigate to source item from linked item via 'Locate Source File' from cotnext menu. Works with vs2010 and vs2012.
It appears that when you "Add Existing" to a SOLUTION FOLDER(as opposed to an actual folder), then you are always adding these items as a link. If you add existing items to an actual folder, then you get the button that gives the option for "Add as Link".
Simply Edit project file and change the path of the file. You can relatively move folder up using ../ It starts in the project folder.
I found an nice tip here: If you want to add an existing item as link in VS C# Express 2010 in the "Add existing item" dialog you have to explicitly choose Add As Link from the dropdown on the Add button.
来源：https://stackoverflow.com/questions/11767269/add-existing-item-in-visual-studio-is-it-possible-to-make-add-as-link-defau