C# dynamic multidimensional list or array

Question

I need to create a list (array or any type) that would hold values, but these values would vary in size. I'm not sure what data type to use in C#. In PHP it would be something like this;

$a = [1,2];
$a[] = 3;
$a[][] = [4,5,6]; // This would hold any number of values
$a[] = 7;
$a[][] = [8,9];   // This would hold any number of values

The result would be an 'array' that could hold any number of values like this: See how index 3 is also an array that could hold any number of values. The same is for index 5.

> Array (
>     [0] => 1
>     [1] => 2
>     [2] => 3
>     [3] => Array
>         (
>             [0] => Array
>                 (
>                     [0] => 4
>                     [1] => 5
>                     [2] => 6
>                 )
> 
>         )
> 
>     [4] => 7
>     [5] => Array
>         (
>             [0] => Array
>                 (
>                     [0] => 8
>                     [1] => 9
>                 )
> 
>         )
> 
> )

I tried this way, but it doesn't work:

int[,] array2D = new int[,] { { 1, 2 }, { 3 }, { 4, 5, 6 }, { 7, 8 } };

Answer 1

Well, since you only have two options: Int or IEnumerable<Int>, you could do something like...

public class IntContainer {
   private Int _intValue;
   private IEnumerable<Int> _intCollection;

   public IntContainer(Int val) {
      this._intValue = val;
   }


   public IntContainer(IEnumerable<Int> val) {
      this._intCollection = val;
   }

   public bool IsSingleValue() => _intCollection == null;
   public bool IsMultiValue() => _intCollection != null;
}

Then have a List<IntContainer> like so:

var myList = new List<IntContainer>{
new IntContainer(new [] { 1, 2})
};

myList.Add(new IntContainer(3));

myList.Add(new IntContainer(new [] { 4,5,6 })); // etc..

Note: the real difference is not between PHP and C#, but between statically typed and dynamically typed languages.

Answer 2

This comes close to what you want

int[][] x =  { new[]{1, 2 }, new[]{ 3 }, new[]{ 4, 5, 6 }, new[]{ 7, 8 } };

All top level elements will be arrays, so x[1] is not 3 but an array with 1 element.

x[0][0] = 1;
x[1][0] = 3;
//Note: x[1][1] => 'x[1][1]' threw an exception of type 'System.IndexOutOfRangeException'

---

In your question you have

> Array (
>     [0] => 1
>     [1] => 2
>     [2] => 3

but then you try to declare it{ { 1, 2 }, { 3 },.

You can achieve both with

int[][] x =  { new[]{1, 2 }, new[]{ 3 }, new[]{ 4, 5, 6 }, new[]{ 7, 8 } };

vs

int[][] x =  { new[]{1}, new[]{2}, new[]{ 3 }, new[]{ 4, 5, 6 }, new[]{ 7, 8 } };

Answer 3

As I mentioned doing things like PHP in C# is not the best way of doing it since you are not using c# to it's fullest power. But if you are use to dynamic types there is a way to do it in c# as well. You can create something similar to PHP with dynamic keyword.

 dynamic data = new dynamic[] 
            { 
                new[] { 1, 2 },  
                3, 
                new[] { 4, 5, 6 }, 
                new[] { 7, 8 } 
            };

            Console.WriteLine(data[0][0] + data[1]);

But it would not be the same as PHP because Array is not an actual array it's a map.

For the even more PHP "Array" you could use a dictionary

dynamic a = new Dictionary<dynamic, dynamic>()
            {
                [0] = 1,
                [1] = 2,
                [2] = 3,
                [3] = new Dictionary<dynamic, dynamic>()
                {
                    [0] = new Dictionary<dynamic, dynamic>()
                    {
                        [0] = 4,
                        [1] = 5,
                        [2] = 6,
                    }
                },
                [4] = 7,
                [5] = new Dictionary<dynamic, dynamic>()
                {
                    [0] = new Dictionary<dynamic, dynamic>()
                    {
                        [0] = 8,
                        [1] = 9
                    }

                }
            };

but this will throw exceptions when you try to access an element out of range but you could implement your own dictionary quite ease to solve this problem. BUT I think this is not really C# way of doing it and might want to rethink what you are trying to do.