Can I add a where clause to an IOrderedEnumerable list?

Question

I have a list of arrays. Each array consists of a score and a difficulty. Read in from a text file.

This is how I get the data and order it by the score in descending order.

// load highscores
public void LoadScores()
{
    // loop through each line in the file
    while ((line = file.ReadLine()) != null)
    {
        // seperate the score from the difficulty
        lineData = line.Split(',');

        // add each line to the list
        list.Add(lineData);
    }

    // order the list by descending order
    IOrderedEnumerable<String[]> scoresDesc = list.OrderByDescending(ld => lineData[0]);

}

Is it possible to add the a clause to the IOrderedEnumerable so that it orders by the score in descending order where the difficulty is 1 ?

Yes, since method arguments (this includes extension methods) are polymorphic, and `IOrderedEnumerable` extends `IEnumerable`. The return value will be of type `IEnumerable` though, so you might want to filter before you use `OrderByDescending`. — Asad Saeeduddin, Apr 29 '14 at 13:40

score 2 · Accepted Answer · answered Apr 29 '14 at 13:49

2

Assuming the "difficulty" is the second item in the array:

 IEnumerable<String[]> scoresDesc =
     list.OrderByDescending(ld => lineData[0])
         .Where(ld => lineData[1] == 1);

You can sort it afterwards, but Where returns an IEnumerable<T>, not an IOrderedEnumerable<T>, so if you need it to be an IOrderedEnumerable<T> then it's cleaner (and faster) to filter the list first:

 IOrderedEnumerable<String[]> scoresDesc =
     list.Where(ld => lineData[1] == 1)
         .OrderByDescending(ld => lineData[0]);

(this is where var eases some pain, since you aren't bound to the return type)

answered Apr 29 '14 at 13:49

D Stanley

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`IEnumerable ScoresDes = list.OrderByDescending(ld => lineData[0]).Where(ld => lineData[1] == 1);` gives me this warning `operator '==' cannot be applied to operands of type 'string' and 'int'. What do I need to do here? – crmepham Apr 29 '14 at 14:47
I seemed to fix this using `IEnumerable ScoresDes = list.OrderByDescending(ld => lineData[0]).Where(ld => lineData[1].Contains("1"));` or atleast I don't get any errors. – crmepham Apr 29 '14 at 14:54
If `lineData[1]` is a string then `lineData[1] == "1"` is appropriate. Otherwise it will pick up `"10"`, `"11"`, `"12"`, `"21"`, etc. – D Stanley Apr 29 '14 at 14:58

score 0 · Answer 2 · answered Apr 29 '14 at 13:39

0

If you want to filter for those of difficulty 1, you can use the .Where() extension method, if you want to sort by more than one field, you can use the .ThenBy() extension method.

answered Apr 29 '14 at 13:39

nvoigt

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score 0 · Answer 3 · answered Apr 29 '14 at 13:43

0

first filter then order:

list.Where(x => x.difficulty == 1).OrderByDescending(ld => lineData[0]);

answered Apr 29 '14 at 13:43

Ashok Damani

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where you have `x.difficulty` how do I name my array index diffculty like this? – crmepham Apr 29 '14 at 14:33

Can I add a where clause to an IOrderedEnumerable list?

3 Answers3