public TextChangeArgs(ITextSnapshot oldSnapshot, Span oldSpan, ITextSnapshot newSnapshot, Span newSpan)
		{
			OldSnapshot = oldSnapshot;
			OldSpan = oldSpan;
			NewSnapshot = newSnapshot;
			NewSpan = newSpan;
		}
		public static void Delete(this ITextViewDocument document, Span span)
		{
			document.Buffer.Delete(span.Start, span.Length);
		}
		public TextSpan(ITextSnapshot snapshot, Span span)
		{
			Snapshot = snapshot;
			Span = span;
		}