Equivalent of Math.Min & Math.Max for Dates?

Question

What's the quickest and easiest way to get the Min (or Max) value between two dates? Is there an equivalent to Math.Min (& Math.Max) for dates?

I want to do something like:

 if (Math.Min(Date1, Date2) < MINIMUM_ALLOWED_DATE) {
      //not allowed to do this
 }

Obviously the above Math.Min doesn't work because they're dates.

Answer 1

There's no built in method to do that. You can use the expression:

(date1 > date2 ? date1 : date2)

to find the maximum of the two.

You can write a generic method to calculate Min or Max for any type (provided that Comparer<T>.Default is set appropriately):

public static T Max<T>(T first, T second) {
    if (Comparer<T>.Default.Compare(first, second) > 0)
        return first;
    return second;
}

For the sake of fun, you can use LINQ too:

new[]{date1, date2, date3}.Max()

Answer 2

How about:

public static T Min<T>(params T[] values)
{
    if (values == null) throw new ArgumentNullException("values");
    var comparer = Comparer<T>.Default;
    switch(values.Length) {
        case 0: throw new ArgumentException();
        case 1: return values[0];
        case 2: return comparer.Compare(values[0],values[1]) < 0
               ? values[0] : values[1];
        default:
            T best = values[0];
            for (int i = 1; i < values.Length; i++)
            {
                if (comparer.Compare(values[i], best) < 0)
                {
                    best = values[i];
                }
            }
            return best;
    }        
}
// overload for the common "2" case...
public static T Min<T>(T x, T y)
{
    return Comparer<T>.Default.Compare(x, y) < 0 ? x : y;
}

Works with any type that supports IComparable<T> or IComparable.

Actually, with LINQ, another alternative is:

var min = new[] {x,y,z}.Min();

Answer 3

There is no overload for DateTime values, but you can get the long value Ticks that is what the values contain, compare them and then create a new DateTime value from the result:

new DateTime(Math.Min(Date1.Ticks, Date2.Ticks))

(Note that the DateTime structure also contains a Kind property, that is not retained in the new value. This is normally not a problem; if you compare DateTime values of different kinds the comparison doesn't make sense anyway.)