How to get only odd arguments

Question

I am trying to get only odd arguments in a list. Here is a piece of my code

static void Main(string[] args)
{
     var swictches = args.ToList().Select((x, index) => (index % 2) == 1);
     var ss = swictches[0];

     string test = doc.ReadAllPages();
     Console.WriteLine(test.Substring(0, 1000));
     Console.Read();
}

In the arguments list it has switches and parameters. I am trying to get all the switches. When I run this code the switches variable looks like this:

false
true
false

instead of like this

-i
-awq
-l

And if you just need the first item use `First`, rather than calling `ToList` on the query just to get the first item. — Servy, Sep 09 '13 at 19:56
The better idea: use a [commandline-switches library](http://stackoverflow.com/a/2067916). — H H, Sep 09 '13 at 19:56

MarcinJuraszek · Accepted Answer · 2013-09-09T19:59:24.937

Use Where instead of Select:

var swictches = args.Where((x, index) => (index % 2) == 1).ToList();

Where filters items based on specified predicate.
Select projects elements from one format into another (from string to bool in your code).

Also, you don't have to call ToList() to use Where/Select. string[] implements IEnumerable<string> as well, so you can just use LINQ on it. Instead of calling ToList at the beginning call it as the last method, to instantiate results into List<string>.

Edit:

As pointed in comments. You should use First when you need just the first element from sequence, instead of calling ToList() and using [0] on the results. It's will be faster:

var ss = args.Where((x, index) => (index % 2) == 1).First();

score 2 · Answer 2 · answered Sep 09 '13 at 20:06

2

var switchesFixed = args.Where((item, index) => index % 2 != 0); //returns Even args

var switchesFixed = args.Where((item, index) => index % 2 == 0); //returns Odd args

answered Sep 09 '13 at 20:06

Qui_Jon

163
1
10

score 1 · Answer 3 · answered Sep 09 '13 at 20:00

1

Another variant to find all switches:
args.Where(s => s.StartsWith("-")).ToList()

answered Sep 09 '13 at 20:00

Vladimir

7,345
4
34
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How to get only odd arguments

3 Answers3