Create a file called c:\crap.txt of exactly one megabyte in size filled with the following data.

1234567890123456789012345... etc

Hints
File.CreateText("") is useful for creating new files on disk, it returns a StreamWriter object
The StreamWriter object has a Write("") method which can be used to write a string to the stream.
When you have finished with a Stream it must be closed using the Close() method.