C# Create Const Array with multiple values at once

Question

I have class like below;

public class PhoneNumbersDto
{            
 public string code { get; set; }
 public int dial { get; set; }
 public string mask { get; set; }
 public string name { get; set; }
}

And I have Values like below;

 {
    "code": "TR",
    "dial": 90,
    "mask": "### ### ## ##",
    "name": "Turkey"
  },
  {
    "code": "TM",
    "dial": 993,
    "mask": "## ######",
    "name": "Turkmenistan"
  },
  {
    "code": "TC",
    "dial": 1649,
    "mask": "### ####",
    "name": "Turks & Caicos Islands"
  }

I want to create a static const array with TheseClassType but i couldn't initilize it.

Is there a way to create static or const array with multiple values at once.

Thank you

I created an static array but only with one item. But i could'nt create with multiple array at once. I couldn't find soliton maybe i'm bad to search about solution. — Cemal
– Cemal, Commented Apr 1, 2020 at 21:49

Sean Skelly · Accepted Answer · 2020-04-01 22:01:02Z

3

    public static readonly PhoneNumbersDto[] array =
    {
        new PhoneNumbersDto()
        {
            code = "TR",
            dial = 90,
            mask = "### ### ## ##",
            name = "Turkey"
        },
        new PhoneNumbersDto()
        {
            code = "TM",
            dial = 993,
            mask = "## ######",
            name = "Turkmenistan"
        },
        new PhoneNumbersDto()
        {
            code = "TC",
            dial = 1649,
            mask = "### ####",
            name = "Turks & Caicos Islands"
        }
    };

As @eocron said, initialization can work; above is an example. Though for better style, I recommend that you use a constructor taking these four inputs, rather than the style shown.

readonly is used in place of const - you can only declare compile-time items as constants. readonly just means you can't edit the reference to this array.

answered Apr 1, 2020 at 22:01

Sean Skelly

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3 Comments

madreflection Over a year ago

For completeness, it should be pointed out that the array elements can be changed, even though the array reference itself cannot. If complete immutability is required, ReadOnlyCollection<PhoneNumbersDto> or a similar type should be used (which could be initialized from the expression shown here, except you would need an explicit new).

Sean Skelly Over a year ago

@madreflection: absolutely right. There are a lot of design improvements that can be made here, including the decision of this being a static field in the first place. Perhaps a method returning a ReadOnlyCollection could be better. Hopefully this is a step in the right direction.

madreflection Over a year ago

It's more about information (answer) improvement than anything to do with the design. You say that "you can't edit the reference to this array", and you're correct, but a novice might incorrectly assume that the statement extends to array elements. So to prevent that assumption from lasting past that statement, it's good to point out the difference.

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