Question

Here is some sample code:

IList<MyType> myList1=new List<MyType>();
IList<MyType> myList2=new List<MyType>();

// Populate myList1
...
// Add contents of myList1 to myList2
myList2.Add(myList1); // Does not compile

How do I add the contents of one list to another – is there a method for this?

Answer 1

There’s no great built-in way to do this. Really what you want is an AddRange method but it doesn’t exist on the IList<T> (or it’s hierarchy). Defining a new extension method though for this is straight forward

public static void AddRange<T>(this ICollection<T> collection, IEnumerable<T> enumerable) {
  foreach (var cur in enumerable) {
    collection.Add(cur);
  }
}

myList2.AddRange(myList1);