DateDiff() function in C#

I have written the following DateDiff() function in C#. VB.NET users already had it using the Micrsoft.VisualBasic.dll assembly. Now you can use it without referencing this ‘ugly’ extra assembly.

using System; 

namespace PureSourceCode.System 
{ 
    public enum DateInterval 
    { 
        Year, 
        Month, 
        Weekday, 
        Day, 
        Hour, 
        Minute, 
        Second 
    } 
    
    public class DateTimeUtil 
    { 
        public static long DateDiff(DateInterval interval, DateTime date1, DateTime date2) 
        { 
            TimeSpan ts = date2 - date1; 
            switch (interval) 
            { 
                case DateInterval.Year: 
                    return date2.Year - date1.Year; 
                case DateInterval.Month: 
                    return (date2.Month - date1.Month) + (12 * (date2.Year - date1.Year)); 
                case DateInterval.Weekday: 
                    return Fix(ts.TotalDays) / 7; 
                case DateInterval.Day: 
                    return Fix(ts.TotalDays); 
                case DateInterval.Hour: 
                    return Fix(ts.TotalHours); 
                case DateInterval.Minute: 
                    return Fix(ts.TotalMinutes); 
                default: 
                    return Fix(ts.TotalSeconds); 
            } 
        } 
        
        private static long Fix(double Number) 
        { 
            if (Number >= 0) 
            { 
                return (long)Math.Floor(Number); 
            } 
            return (long)Math.Ceiling(Number); 
        } 
    } 
}