List ordering - Extension method not firing!

Question

Hi All,

I am trying to sort a List like this:

public void Example()
{
    string target = "hello";

    List<string> myStings = new List<string>();

    myStings.Add("babab");
    myStings.Add("Helll");
    myStings.Add("atest");

    myStings.OrderBy(each => Distance(each, target));
}

public int Distance(string stringA, string stringB)
{
    // Whatever
}

The problem is that the list doesn't get ordered and the Distance method doesn't get fired (I put a breakpoint in there but doesn't get hit).

Any help appreciated!

Answer 1

myStings = myStings.OrderBy(each => Distance(each, target)).ToList();

Answer 2

This is because of Linq's Deferred Execution

In LINQ, execution of a query is usually deferred until the moment when you actually request the data.

So, to see your method working, apply the ToList() method to your IOrderedEnumerable so that you will actually be requesting the data, and thus the execution takes place.

myStings = myStings.OrderBy(each => Distance(each, target)).ToList();

Answer 3

your

myStrings.OrderBy(each => Distance(each, target));

wont order your original list it return a ordered list. You need:

myStrings = myStrings.OrderBy(each => Distance(each, target)).ToList();

this will force the deferred execution to take place and give you the result you require.