LINQ: How do I concatenate a list of integers into comma delimited string?

It's probably something silly I missed, but I try to concatenate a list of integers instead of summing them with:

integerArray.Aggregate((accumulator, piece) => accumulator+"," + piece)

The compiler complained about argument error. Is there a slick way to do this without having to go through a loop?

Which version of .NET? In 4.0 you can use string.Join(",",integerArray). In 3.5 I would be tempted to just use string.Join(",",Array.ConvertAll(integerArray,i=>i.ToString())); (assuming it is an array). Otherwise, either make it an array, or use StringBuilder.

You probably want to use String.Join.

string.Join(",", integerArray.Select(i => i.ToString()).ToArray());

If you're using .Net 4.0, you don't need to go through the hassle of reifying an array. and can just do

 string.Join(",", integerArray);

The error you are getting is because you didn't use the override of Aggregate which lets you specify the seed. If you don't specify the seed, it uses the type of the collection.

integerArray.Aggregate("", (accumulator, piece) => accumulator + "," + piece);

Just to add another alternative to @Marc's

var list = string.Join( ",", integerArray.Select( i => i.ToString() ).ToArray() );