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Add Existing Project Command
Adds an existing project to the current solution.
Optional. The full path and project name, with extension, of the project to add to the solution.
If the filename argument includes spaces, it must be enclosed in quotation marks.
If no filename is specified, the command will open the file dialog so that user can pick a project.
Auto completion tries to locate the correct path and file name as you type.
This example adds the Visual Basic project, TestProject1, to the current solution.
>File.AddExistingProject "c:\visual studio projects\TestProject1.vbproj"