CODEWITHSUNDEEP
c#.netlinqgenerics
iLemming
iLemming

Reputation: 36166

Simple LINQ query

I have a collection like this

 List<int> {1,15,17,8,3};

how to get a flat string like "1-15-17-8-3" through LINQ query?

thank you

Upvotes: 0

Views: 382

Answers (5)

LukeH
LukeH

Reputation: 269298

The best answer is given by Tim J.

If, however, you wanted a pure LINQ solution then try something like this (much more typing, and much less readable than Tim J's answer):

string yourString = yourList.Aggregate
    (
        new StringBuilder(),
        (sb, x) => sb.Append(x).Append("-"),
        sb => (sb.Length > 0) ? sb.ToString(0, sb.Length - 1) : ""
    );

(This is a variation on Charles's answer, but uses a StringBuilder rather than string concatenation.)

Upvotes: 0

Charles
Charles

Reputation: 6307

Use Enumerable.Aggregate like so:

var intList = new[] {1,15,17,8,3};

string result = intList.Aggregate(string.Empty, (str, nextInt) => str + nextInt + "-");

This is the standard "LINQy" way of doing it - what you're wanting is the aggregate. You would use the same concept if you were coding in another language, say Python, where you would use reduce().

EDIT: That will get you "1-15-17-8-3-". You can lop off the last character to get what you're describing, and you can do that inside of Aggregate(), if you'd like:

string result = intList.Aggregate(string.Empty, (str, nextInt) => str + nextInt + "-", str => str.Substring(0, str.Length - 1));

The first argument is the seed, the second is function that will perform the aggregation, and the third argument is your selector - it allows you to make a final change to the aggregated value - as an example, your aggregate could be a numeric value and you want return the value as a formatted string.

HTH,

-Charles

Upvotes: 1

a7drew
a7drew

Reputation: 7821

You can write an extension method and then call .ToString("-") on your IEnumerable object type as shown here:

int[] intArray = { 1, 2, 3 };
Console.WriteLine(intArray.ToString(","));
// output 1,2,3

List<string> list = new List<string>{"a","b","c"};
Console.WriteLine(intArray.ToString("|"));
// output a|b|c

Examples of extension method implementation are here:

http://coolthingoftheday.blogspot.com/2008/09/todelimitedstring-using-linq-and.html http://www.codemeit.com/linq/c-array-delimited-tostring.html

Upvotes: 1

Tim Jarvis
Tim Jarvis

Reputation: 18815

something like...

string mystring = string.Join("-", yourlist.Select( o => o.toString()).toArray()));

(Edit: Now its tested, and works fine)

Upvotes: 9

Andrew Siemer
Andrew Siemer

Reputation: 10278

StringBuilder sb = new StringBuilder();

foreach(int i in collection)
{
    sb.Append(i.ToString() + "-");
}

string result = sb.ToString().SubString(0,sb.ToString().ToCharArray().Length - 2);

Something like this perhaps (off the top of my head that is!).

Upvotes: 0

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