Shortest way to create a List<T> of a repeated element

Question

With the String class, you can do:

string text = new string('x', 5);
//text is "xxxxx"

What's the shortest way to create a List< T > that is full of n elements which are all the same reference?

Solution 1

Try the following

var l = Enumerable.Repeat('x',5).ToList();

Solution 2

Fastest way I know is:

int i = 0;
MyObject obj = new MyObeject();
List<MyObject> list = new List<MyObject>();
for(i=0; i< 5; i++)
{
    list.Add(obj);
}

which you can make an extention method if you want to use it multiple times.

public void AddMultiple(this List<T> list, T obj, int n)
{
    int i;
    for(i=0;i<n;i++)
    {
        list.Add(obj);
    }
}

Then you can just do:

List<MyObject> list = new List<MyObject>();
MyObject obj = new MyObject();
list.AddMultiple(obj, 5);

Solution 3

This seems pretty straight-forward ...

for( int i = 0; i < n; i++ ) { lst.Add( thingToAdd ); }

:D

Comments

[xyz]

I know how to do it. I said shortest.

[xyz]

I wasn't one to downvote you, btw. Easy mistake given I didn't say it in the title. Updated it :)

[JP Alioto]

np ... I wonder what you definition of shortest is? Minified?

[typpo]

If you know the list length, set it during construction: var list = new List<MyObject>(5);

[user1234567]

#Note: for reference type it results in a list of 5 references to same instance. E.g.: var l = Enumerable.Repeat(new SomeRefType(),5).ToList(); will create single instance of SomeRefType & populate list with 5 references to this instance.