Suppose I have two functions which look like this:

public static void myFunction1(int a, int b, int c, string d)
{
    //dostuff
    someoneelsesfunction(c,d);
    //dostuff2
}

public static void myFunction2(int a, int b, int c, Stream d)
{
    //dostuff
    someoneelsesfunction(c,d);
    //dostuff2
}

What would be a good way to avoid repeated dostuff?

Ideas I've thought of, but don't like:

1. I could make d an object and cast at runtype based on type, but this strikes me as not being ideal; it removes a type check which was previously happening at compile time.
2. I could also write a private helper class that takes an object and write both signatures as public functions.
3. I could replace dostuff and dostuff2 with delegates or function calls or something.