Your error message allready says whats wrong.
You call the function with two arguments:
ReadJpeg(myStream, String.Empty).
But according to your function definition it expects only 1 argument:
public static JpegInfo ReadJpeg(FileInfo fi)
In fact it expects totally different variable types your trying to call it with ... did you really write this yourself?
There also is no overloaded version of the function which fits the argument list you called the function with.