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Answer 1

+5 A:

This should do the trick

List<Type> list1;
List<Type> list2;

List<Type> combined;
combined.AddRange(list1);
combined.AddRange(list2);

Timo Willemsen 2010-01-04 22:36:05

Is this the most efficient, or the most convenient way?

Hamish Grubijan 2010-01-04 22:37:38

pstst .AddRange, Java is over there ->

blu 2010-01-04 22:39:10

@Ipthnc, I dont know a other way to do it, other than a `foreach()` combined with `List.Add()`. But it sure is the most convenient way.

Timo Willemsen 2010-01-04 22:39:59

@gah. Heh im programming java right now. Annoying naming conventions.

Timo Willemsen 2010-01-04 22:40:51

Why not just do list1.AddRange(list2)? It meets the requirements without having to create an additional list, and saves an entire add.

Erich 2010-01-04 22:43:42

@Erich, that sure is a better way. My example just demonstrated the use.

Timo Willemsen 2010-01-04 22:45:22

Err, *no*, that's not necessarily a better way. You're assuming that it's OK to modify the first list (for that matter, why not do it to the second list instead?) when that's not made clear.

Adam Robinson 2010-01-04 22:46:31

Indeed, that's the assumtion me and Erich made. I have to adjust my opinion on that one. Assuming it is okay to modify the first list, it is faster.

Timo Willemsen 2010-01-04 22:50:10

Answer 2

+1 A:

Using the .AddRange() method

http://msdn.microsoft.com/en-us/library/z883w3dc.aspx

Computer Linguist 2010-01-04 22:36:57

Answer 3

+3 A:

If you're using C# 3.0/.Net 3.5:

List<SomeType> list1;
List<SomeType> list2;

var list = list1.Concat(list2).ToList();

Rafa Castaneda 2010-01-04 22:40:06

As a clarification, this requires .NET 3.5, not just C# 3.0 (extension methods are a part of C# 3.0, but the `System.Linq.Enumerable` class that defines them is part of .NET 3.5)

Adam Robinson 2010-01-04 22:45:15

@Adam Robinson: Thanks for the precision.

Rafa Castaneda 2010-01-04 22:52:52

This can work on .NET 2.0 if you use VS2008 and LinqBridge ;)

Thomas Levesque 2010-01-04 23:22:40

Answer 4

+4 A:

You can simply add the items from one list to the other:

list1.AddRange(list2);

If you want to keep the lists and create a new one:

List<T> combined = new List<T>(list1);
combined.AddRange(list2);

Or using LINQ methods:

List<T> combined = list1.Concat(list2).ToList();

You can get a bit better performance by creating a list with the correct capacity before adding the items to it:

List<T> combined = new List<T>(list1.Count + list2.Count);
combined.AddRange(list1);
combined.AddRange(list2);

Guffa 2010-01-04 22:49:23

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.NET: Combining two generic lists.

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