ASP.NET MVC help with MemoryStream

I need to generate a file (.txt) using memory stream, i have a list string... example: string[] = {"line 1", "line 2", "line 3"} and i need a file like this: line 1 line 2 line 3 Is not in the same line, always break. the problem is i dont know how to work with MemoryStream(), PS: I need to generate a .txt file if you know a better way its welcome