c# - Replace multiple InsertRange() into efficient way

Question

Inserting items to a collection,

MyList.Clear();
MyList.InsertRange(MyList.Count, Collection1);
MyList.InsertRange(MyList.Count, Collection2);
MyList.InsertRange(MyList.Count, Collection3);

In the above code, I am inserting 3 times to the same list in order to follow the sequence. Can this be replaced efficiently?

Answer 1

Not sure if this is more efficient:

MyList.AddRange(Collection1.Concat(Collection2).Concat(Collection3));

If the collections are large it will probably more efficient if you prepend this line:

MyList = new List<string>(Collection1.Count + Collection2.Count + Collection3.Count);

(presumed it's a List<string>)