How to Sort a List by a property in the object

Question

I have a class called Order which has properties such as OrderId, OrderDate, Quantity, and Total. I have a l

Answer 1

To do this without LINQ on .Net2.0:

List objListOrder = GetOrderList();
objListOrder.Sort(
    delegate(Order p1, Order p2)
    {
        return p1.OrderDate.CompareTo(p2.OrderDate);
    }
);

If you're on .Net3.0, then LukeH's answer is what you're after.

To sort on multiple properties, you can still do it within a delegate. For example:

orderList.Sort(
    delegate(Order p1, Order p2)
    {
        int compareDate = p1.Date.CompareTo(p2.Date);
        if (compareDate == 0)
        {
            return p2.OrderID.CompareTo(p1.OrderID);
        }
        return compareDate;
    }
);

This would give you ascending dates with descending orderIds.

However, I wouldn't recommend sticking delegates as it will mean lots of places without code re-use. You should implement an IComparer and just pass that through to your Sort method. See here.

public class MyOrderingClass : IComparer
{
    public int Compare(Order x, Order y)
    {
        int compareDate = x.Date.CompareTo(y.Date);
        if (compareDate == 0)
        {
            return x.OrderID.CompareTo(y.OrderID);
        }
        return compareDate;
    }
}

And then to use this IComparer class, just instantiate it and pass it to your Sort method:

IComparer comparer = new MyOrderingClass();
orderList.Sort(comparer);