How do I create a file AND any folders, if the folders don't exist?

To summarize what has been commented in other answers:

//path = @"C:\Temp\Bar\Foo\Test.txt";
Directory.CreateDirectory(Path.GetDirectoryName(path));

Directory.CreateDirectory will create the directories recursively and if the directory already exist it will return without an error.

If there happened to be a file Foo at C:\Temp\Bar\Foo an exception will be thrown.

DirectoryInfo di = Directory.CreateDirectory(path);
Console.WriteLine("The directory was created successfully at {0}.",
    Directory.GetCreationTime(path));

See this MSDN page.

Hope that helps out!

Use Directory.CreateDirectory before you create the file. It creates the folder recursively for you.