How to Sort a List<T> by a property in the object
I have a class called Order which has properties such as OrderId , OrderDate , Quantity , and Total . I have a list of this Order class:
List<Order> objListOrder = new List<Order>();
GetOrderList(objListOrder); // fill list of orders
Now I want to sort the list based on one property of the Order object, for example I need to sort it by the order date or order id.
How can i do this in C#?
我能想到的最简单的方法是使用Linq：
List<Order> SortedList = objListOrder.OrderBy(o=>o.OrderDate).ToList();
If you need to sort the list in-place then you can use the Sort method, passing a Comparison<T> delegate:
objListOrder.Sort((x, y) => x.OrderDate.CompareTo(y.OrderDate));
If you prefer to create a new, sorted sequence rather than sort in-place then you can use LINQ's OrderBy method, as mentioned in the other answers.
To do this without LINQ on .Net2.0:
List<Order> 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<Order>
{
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<Order> comparer = new MyOrderingClass();
orderList.Sort(comparer);
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