Question

I have a list of XElement Objects in c#. Each XElement object has attribute index, something like this :

<A index="2" .... ></A>
<B index="4" .....></B>
...
.. 

Now i want to sort these elements in ascending order according to its index value. For this i tried :

 listOfElement.OrderBy(e => e.Attribute("index").Value);

But the elements are not sorted in the list. What i am doing wrong here ?

Answer 1

First, you’re not casting the value to an int. It’s harmless in this case, but you might want to do:

e => (int)e.Attribute("index")

Secondly, the OrderBy doesn’t do side-effect on the type it operates on, but it returns a new IEnumerable<T>. You can overwrite your previous list by writing:

 listOfElement = listOfElement.OrderBy(e => (int)e.Attribute("index")).
                     ToList();

Alternatively, you can use the List<T>.Sort(Comparison<XElement>) method in this way:

listOfElement.Sort((e1, e2) => 
            (int)e1.Attribute("index") - (int)e2.Attribute("index"));