Adding multiple values on list

Question

Is it possible to add multiple items into list or adding a list of values into a list.

here is my current pseudo code to do it:

List<string> myList = new List<string>();
myList.add("a","b","c","d","e","f","g");       
myList.add("h","i","j","k","l","m","n");       
myList.add("a1","a2","a3");

and my expected result is:

[["a","b","c","d","e","f","g"], ["h","i","j","k","l","m","n"], ["a1","a2","a3"]]

Any suggestions/comments TIA.

yes that's what I want because later on I will loop it and then just get selected index on each list. — Syntax Rommel
– Syntax Rommel, Commented Apr 2, 2019 at 1:58

DavidG · Accepted Answer · 2019-04-02 02:06:33Z

3

What you are asking for is a List<List<string>>. There are probably better structures for storing your data but since you haven't given any context, you can do this:

var myList = new List<List<string>>();

And add items like this:

myList.Add(new List<string> { "a", "b", "c", "d", "e", "f", "g" });
myList.Add(new List<string> { "h", "i", "j", "k", "l", "m", "n" });
myList.Add(new List<string> { "a1", "a2", "a3" });

Or in one piece of code using a collection initialiser:

var myList = new List<List<string>>
{
    new List<string> { "a", "b", "c", "d", "e", "f", "g" },
    new List<string> { "h", "i", "j", "k", "l", "m", "n" },
    new List<string> { "a1", "a2", "a3" }
};

edited Apr 2, 2019 at 2:06

answered Apr 2, 2019 at 2:03

DavidG

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6 Comments

Mick Over a year ago

You could also use the AddRange method to add more than one value at a time.

DavidG Over a year ago

@Mick I'm not sure AddRange makes the code any more readable in this situation. We would need to create an IEnumerable which is unnecessary.

vasily.sib Over a year ago

@DavidG, I think that Mick is talking about replacing 3x myList.Add(new List<string> { .. } with myList.AddRange(new [] { new List<string> { .. }, new List<string> { .. }, new List<string> { .. } }); which looks just like collection initializer.

DavidG Over a year ago

@vasily.sib Yes, and I'm saying that's a horrible way to do it. That creates an intermediate array object that isn't needed, and I think makes it less readable.

vasily.sib Over a year ago

@DavidG, can you pls explain what is so horrible with that? With just a little formatting this will look almost the same as collection initializer and an intermediate array object will be disposed by GC as soon as posible. Beside that, question was about adding values to the list, so AddRange example looks handy.

|

TheGeneral · Accepted Answer · 2019-04-02 02:07:55Z

Should be as easy as

var myList = new List<List<string>>()
         {
            new List<string> { "a", "b", "c", "d", "e", "f", "g" },
            new List<string> { "h", "i", "j", "k", "l", "m", "n" },
            new List<string> { "a1", "a2", "a3" },
         };
// OR

var myarray = new[]
          {
             new[] { "a", "b", "c", "d", "e", "f", "g" },
             new[] { "h", "i", "j", "k", "l", "m", "n" },
             new[] { "a1", "a2", "a3" },
          };

Additional Resources

Object and Collection Initializers (C# Programming Guide)

C# lets you instantiate an object or collection and perform member assignments in a single statement.

Collection initializers

Collection initializers let you specify one or more element initializers when you initialize a collection type that implements IEnumerable and has Add with the appropriate signature as an instance method or an extension method. The element initializers can be a simple value, an expression, or an object initializer. By using a collection initializer, you do not have to specify multiple calls; the compiler adds the calls automatically.

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