System.Web.HttpResponse.GetNormalizedFileName C# (CSharp) Method

		string GetNormalizedFileName (string fn)
		{
			if (String.IsNullOrEmpty (fn))
				return fn;

			// On Linux we don't change \ to / since filenames with \ are valid. We also
			// don't remove drive: designator for the same reason.
			int len = fn.Length;
			if (len >= 3 && fn [1] == ':' && IsFileSystemDirSeparator (fn [2]))
				return Path.GetFullPath (fn); // drive-qualified absolute file path

			if (len >= 2 && IsFileSystemDirSeparator (fn [0]) && IsFileSystemDirSeparator (fn [1]))
				return Path.GetFullPath (fn); // UNC path

			HttpContext ctx = context ?? HttpContext.Current;
			HttpRequest req = ctx != null ? ctx.Request : null;

			if (req != null)
				return req.MapPath (fn);
			
			return fn; // Or should we rather throw?
		}