The :ref:`Visual Studio Generators` create a ``.sln`` file for each directorywhose ``CMakeLists.txt`` file calls the :command:`project` command. Set thisproperty in the same directory as a :command:`project` command call (e.g. inthe top-level ``CMakeLists.txt`` file) to specify the default startup projectfor the correpsonding solution file.
The property must be set to the name of an existing target. Thiswill cause that project to be listed first in the generated solutionfile causing Visual Studio to make it the startup project if thesolution has never been opened before.