[Nerfpl]

Hi

Instead of

List<string> allStrings = new List<string>(){"a","b,"c"};
string o = string.Empty;

foreach(string s in allStrings) o+=s+"\n";

mbox("strings: "+o);

i would like to do something like

mbox("strings: " + allStrings.ForEach(p=>p+"\n")) //of course this is wrong

is it possible?

[AdamSpeight2008]

It'll help you if you look at the methods available on IEnumerable, else well as their type-signatures.

You're after one that takes in an IEnumerable<T> and func and return a U (in your case that'll be a string).
The method will have the follow type-signature.
(IE<T>,(U,T)->U)->U

Spoiler

Have a look a Aggregrate.

This post has been edited by AdamSpeight2008: 14 April 2012 - 11:36 AM

[CodingSup3rnatur@l-360]

Hi,

This should give you the same output as the longer version:

Spoiler

MessageBox.Show("strings: " + allStrings.Aggregate((s1, s2) => s1 + Environment.NewLine + s2) + Environment.NewLine);

Although do bear in mind that it is advisable to use the StringBuilder class for concatenating strings in a loop with any significant number of iterations (10+) to avoid unnecessary memory allocations.

EDIT: Sorry Adam, I didn't see your post there, and sort of gave the game away...

This post has been edited by CodingSup3rnatur@l-360: 14 April 2012 - 12:02 PM

[Nerfpl]

i searched for some examples and i don't quite understand what goes where.

allStrings.Appregate((result,item) => result += "-" + item + "\n")
//Output:
a-b
-c

allstrings.Appregate((i1, i2) => "-" + i1 + "\n" + i2)
//Output
--a
b
c

//And i need
-a
-b
-c

This post has been edited by Nerfpl: 14 April 2012 - 12:08 PM

[CodingSup3rnatur@l-360]

To do that, you would need something like this:

Spoiler

"-" + allStrings.Aggregate((result, item) => result + Environment.NewLine + "-" + item) + Environment.NewLine

Feel free to ask if you don't understand any part of that

[Nerfpl]

CodingSup3rnatur@l-360, on 14 April 2012 - 12:28 PM, said:

To do that, you would need something like this:

Spoiler

"-" + allStrings.Aggregate((result, item) => result + Environment.NewLine + "-" + item) + Environment.NewLine

Feel free to ask if you don't understand any part of that

Well it works but i still don't understand what's going on here, the logic and order. How it would look in raw/expanded form? Is 'Result' really a result and "item' really a current item?

[sepp2k]

Basically enumerable.Aggregate(f, start) is the same as:

var result = start;
foreach(var x in enumerable) {
    result = f(result, x);
}
return result;

If you don't supply a starting value, the first element of the enumerable is used as the starting value (and the iteration starts with the second element). So that's how Aggregate works.

However for this case, I'd just use string.Join:

mbox("strings: " + string.Join("\n", allStrings) + "\n")

You could also use Select in conjunction with Join:

mbox("strings: " + string.Join("", allStrings.Select(s => s + "\n")));

Though in this case I'd prefer the former. Using Select would make more sense if you needed to perform a more complicated transformation on each element.

This post has been edited by sepp2k: 14 April 2012 - 02:11 PM

[Nerfpl]

in

string.Join("", allStrings.Where(s => s + "\n"))

i have 2 errors at 's + "\n"'

• Error 2 Cannot implicitly convert type 'string' to 'bool'
  
• Error 1 Cannot convert lambda expression to delegate type 'System.Func<string,bool>' because some of the return types in the block are not implicitly convertible to the delegate return type

[sepp2k]

Yeah, sorry, I was being stupid. That should have been Select, of course, not Where.

[Nerfpl]

string.Join("\n", duplicates.Select(p => "-"+p))

Works like charm

Thanks!