FileStream and creating folders

Use Directory.CreateDirectory:

Directory.CreateDirectory Method (String)

Creates all directories and subdirectories as specified by path.

Example:

string fileName = @"C:\Users\SomeUser\My Documents\Foo\Bar\Baz\text1.txt";

Directory.CreateDirectory(Path.GetDirectoryName(fileName));

using (FileStream fs = new FileStream(fileName, FileMode.Create))
{
    // ...
}

(Path.GetDirectoryName returns the directory part of the file name.)