Initialization of only few values of c# array?

Question

I am trying to write a program in which, I want to initialize 4 starting values of an array, while the other 16 will be entered manually from the console.

For this I have written the following code:

int[] intArray = new int[20] { 20, 22, 23, 0 };

But I am getting the following exception: "An array initializer of '20' is expected"

I know that it can be done by this syntax :

int[] intArray = new int[20];
intArray[0] = 20;
intArray[1] = 22;
intArray[2] = 23;
intArray[3] = 0;

I would like to know if this can be achieved in one line.

"but i wanna know any how can i do this in one line" - why do you need to? Basically there's no particularly simple way of doing this. There are various ways you could do it with LINQ, but nothing desperately simple. new[] { 20, 22, 23, 0 }.Concat(Enumerable.Repeat(0, 16)).ToArray() would do it, for example... — Jon Skeet
– Jon Skeet, Commented Aug 9, 2015 at 19:11
I assume by one line you mean one statement? Because you could do int[] intArray = new int[20]; intArray[0] = 20; intArray[1] = 22; intArray[2] = 23; intArray[3] = 0; as one line, but it is the same number of statements... — Austin T French
– Austin T French, Commented Aug 9, 2015 at 19:13
yes its working but will you please enplane me how? its working @ jon Skeet — g1ji
– g1ji, Commented Aug 9, 2015 at 19:16

Douglas · Accepted Answer · 2015-08-09 19:26:17Z

2

If you're going to be needing this frequently, you could create your own extension method to populate the values in an existing array:

int[] intArray = new int[20].Populate(20, 22, 23, 0);

Sample implementation:

public static class ListExtensions
{
    public static TList Populate<TList, TElement>(this TList list, params TElement[] values)
        where TList : IList<TElement>
    {
        // TODO: argument validation

        for (int i = 0; i < values.Length; i++)
            list[i] = values[i];

        return list;
    }
}

answered Aug 9, 2015 at 19:26

Douglas

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1 Comment

g1ji Over a year ago

Yes its one of the best and correct way, but i am looking for something as suggested by @jon skeet.

Chris · Accepted Answer · 2015-08-09 21:13:24Z

1

How about keeping it simple:

public static T[] CreateAndInitArray<T>( int len, T[] initialValues )
{
    var temp = new T[len];
    initialValues.CopyTo( temp, 0 );
    return temp;
}

Use:

int[] intArray = CreateAndInitArray( 20, new int[] { 20, 22, 23, 0 } );

The initialValues argument could be a params argument too, but that would easily be confusing considering the length argument. Personally I like the answer Douglas provided better, looks alot more logical.

answered Aug 9, 2015 at 21:13

Chris

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g1ji Over a year ago

yes it's a right way to do the thing i want +1 @chris

TaW · Accepted Answer · 2015-08-10 14:08:08Z

0

This works in two lines:

  int[] intArray = new int[20];
  new int[4] { 20, 22, 23, 0 }.CopyTo(intArray , 0);

Or even:

  int[] intArray = new int[20];
  new int[] { 20, 22, 23, 0 }.CopyTo(intArray , 0);

Note that the unnamed array goes out of scope right after the semicolon.. - I don't think it gets any simpler!

edited Aug 10, 2015 at 14:08

answered Aug 9, 2015 at 19:51

TaW

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Comments

g1ji · Accepted Answer · 2015-08-20 14:56:41Z

0

I found jon skeet suggestion more useful.

new[] { 20, 22, 23, 0 }.Concat(Enumerable.Repeat(0, 16)).ToArray();

answered Aug 20, 2015 at 14:56

g1ji

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Comments

user2884232 · Accepted Answer · 2015-08-09 20:01:19Z

-1

I think that you could do something like this:

    private static int[] getInput()
    {

        int[] array = { 20, 22, 23, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,    1, 1 };

        bool done = false;
        int current = 4;
        while (!done)
        {
            Console.WriteLine("Enter in a number to be added to the array");
            string input = Console.ReadLine();
            array[current] = Convert.ToInt32(input);
            current++;
            if (current==array.Length)
            {
                done = true;
            }
        }
        return array;
    }

answered Aug 9, 2015 at 20:01

user2884232

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