Question

Is there any easy LINQ expression to concatenate my entire List<string> collection items to a single string with a delimiter character?

What if the collection is of custom objects instead of string? Imagine I need to concatenate on object.Name.

Answer 1

Warning – Serious Performance Issues

Though this answer does produce the desired result, it suffers from poor performance compared to other answers here. Be very careful about deciding to use it

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By using LINQ, this should work;

string delimiter = ","; List<string> items = new List<string>() { "foo", "boo", "john", "doe" }; Console.WriteLine(items.Aggregate((i, j) => i + delimiter + j)); 

class description:

public class Foo {     public string Boo { get; set; } } 

Usage:

class Program {     static void Main(string[] args)     {         string delimiter = ",";         List<Foo> items = new List<Foo>() { new Foo { Boo = "ABC" }, new Foo { Boo = "DEF" },             new Foo { Boo = "GHI" }, new Foo { Boo = "JKL" } };          Console.WriteLine(items.Aggregate((i, j) => new Foo{Boo = (i.Boo + delimiter + j.Boo)}).Boo);         Console.ReadKey();      } } 

And here is my best 🙂

items.Select(i => i.Boo).Aggregate((i, j) => i + delimiter + j)