Create duplicate items in a list

Question

I have the following code to duplicate the members of a list X times.

Although it works it doesn\'t feel particularly clean.

Live code example:

Answer 1

You can do this with a little Linq:

int instances = 3;
var serviceEndPoints = 
    (from e in Enumerable.Range(0, instances)
     from x in serviceEndPoints
     select x)
    .ToList();

Or if you prefer fluent syntax:

var serviceEndPoints = Enumerable
    .Range(0, instances)
    .SelectMany(e => serviceEndPoints)
    .ToList();

Note that given a list like { A, B, C } will produce a list like { A, B, C, A, B, C, A, B, C }. If you want to produce a list like { A, A, A, B, B, B, C, C, C }, you can simply reverse the order of the collections:

var serviceEndPoints = 
    (from x in serviceEndPoints
     from e in Enumerable.Range(0, instances)
     select x)
    .ToList();

Or in fluent syntax:

var serviceEndPoints = serviceEndPoints
    .SelectMany(x => Enumerable.Range(0, instances), (x, e) => x)
    .ToList();