IQueryable order by two or more properties

Question

I am currently ordering a list of custom objects using the IQueryable OrderBy method as follows:

mylist.AsQueryable().OrderBy("PropertyName");

Now I am looking to sort by more than one property. Is there any way to do that?

Thanks, Yannis

Answer 1

OrderBy(i => i.PropertyName).ThenBy(i => i.AnotherProperty)

In OrderBy and ThenBy you have to provide keySelector function, which chooses key for sorting from object. So if you know property name only at runtime then you can make such function with Reflection like:

var propertyInfo = i.GetType().GetProperty("PropertyName"); 
var sortedList = myList.OrderBy(i => propertyInfo.GetValue(i, null)) 

But it will be slower, then direct access to property. Also you can "compile" such function on the fly with Linq.Expressions and it will work faster than reflection but it is not very easy. Or you can use CollectionViewSource and their sorting ablilities in WPF.

And don't forget that OrderBy() returns sorted enumerable and it does not sort your existed List inplace. In your example you did not save sorted list to variable.

Answer 2

You could use .ThenBy:

var result = mylist
    .AsQueryable()
    .OrderBy(x => x.PropertyName)
    .ThenBy(x => x.SomeOtherProperty);

Answer 3

You probably want to use the ThenBy extension method to be able to sort by multiple fields

 return myList.AsQueryable().OrderBy(m=>m.Property1).ThenBy(m => m.Property2);

If you want dynamic Linq, look at LinqKit. I recently implemented Microsoft's dynamic Linq library from here and was able to sort by two fields using a string.

Awesome stuff! Not sure if this will be in .NET 5 or not.

Answer 4

As others have suggested, you can use 'ThenBy'. If you want to convert a string to a different value before using it, this is possible too, for example...

    var sortedSystemTestResultsList = systemTestResultsList.OrderBy(s =>
    {
        DateTime dt;
        if (!DateTime.TryParse(s.testPointCompletedDate, out dt)) return DateTime.MaxValue;
        return dt;
    }).ThenBy(s =>
    {
        Int32 tpID;
        if (!Int32.TryParse(s.testRunResultID, out tpID)) return Int32.MaxValue;
        return tpID;
    });