C#: How would you make a unique filename by adding a number?

Question

I would like to create a method which takes either a filename as a string or a FileInfo and adds an incremented number to the filename if the file

Answer 1

/// 

/// Create a unique filename for the given filename
/// 
/// A full filename, e.g., C:\temp\myfile.tmp
/// A filename like C:\temp\myfile633822247336197902.tmp
public string GetUniqueFilename(string filename)
{
    string basename = Path.Combine(Path.GetDirectoryName(filename),
                                   Path.GetFileNameWithoutExtension(filename));
    string uniquefilename = string.Format("{0}{1}{2}",
                                            basename,
                                            DateTime.Now.Ticks,
                                            Path.GetExtension(filename));
    // Thread.Sleep(1); // To really prevent collisions, but usually not needed
    return uniquefilename;
}

As DateTime.Ticks has a resolution of 100 nanoseconds, collisions are extremely unlikely. However, a Thread.Sleep(1) will ensure that, but I doubt that it's needed