I have always found creating solutions using the automation model (EnvDTE) somewhat tricky, because there are two phases: creating the solution and saving the solution to disk, and the methods used to do that are confusing:
– It happens that you have a Solution.Create method, which one would expect to receive only the name of the solution in the Solution Explorer (which is also the base name for the .sln file), but it receives the folder of the solution too, although this method doesn’t save the solution file (.sln) on disk (so, why does it need the folder of the solution?).
– You have also the Solution.SaveAs method, which receives as parameter the name of the .sln file with path, two (combined) pieces of information that you already specified in the Solution.Create method. One would expect a Solution.Save method without parameters. It happens that you have the Solution.Saved property, which is read/write, but I am not sure if you can save the solution setting its value to true.
– Finally, the folder of the solution must exist. Visual Studio doesn’t bother to create it (why?). At least the example of the documentation about Solution2.Create and Solution3.Create warns you, but there is no example if you fall in the SolutionClass.Create or _Solution.Create help pages.
– The confusion is such that the MSDN documentation about the Solution3.Create method lists two “overloaded” methods with the same name and signatures.
I have written the following article which shows also how to get the Visual Studio projects folder, which is the location that you likely want to use to save the solution:
HOWTO: Create a solution from a Visual Studio add-in.