Detecting an empty array without looping

Question

How can i find out an array is empty or not, without looping?!
is there any method or anything else?

I mean, in some code like this:

string[] names = new string[5];
names[0] = "Scott";
names[1] = "jack";
names[2] = null;
names[3] = "Jones";
names[4] = "Mesut";

// or

int[] nums = new int[4];
nums[0] = 1;
// nums[1] = 2;
nums[2] = 3;
nums[3] = 4;

or some code like this:

using System;
class Example
{
    static void Main()
    {
        int size = 10;
        int counter;
        string[] str = new string[size];

        for (counter = 0; counter < size; counter++)
        {
            str[counter] = "A" + counter;
        }

        str[3] = null;

        if (counter == size)
            Console.WriteLine("Our array is full!");
        if(counter < size)
            Console.WriteLine("Our array is not full");

        for (int i = 0; i < size; i++)
        {
            Console.WriteLine(str[i]);
        }
    }
}

is there anything else for detecting an empty array without looping?

Please explain exactly what you mean by an "empty array". Do you mean an array where all items are null? Or an array without any items in it? — Oded
– Oded, Commented Dec 28, 2012 at 12:38
@MesutDarvishian: You need to understand that there's no such thing as "a non-initialized cell" - an array element with a null value is just as "initialized" as an array element with a non-null value. They're both just values. — Jon Skeet
– Jon Skeet, Commented Dec 28, 2012 at 12:42
i mean, in this situation that between names[0] and names[4] just names[2] is null, how can i detect that this array has one null cell? — Masoud Darvishian
– Masoud Darvishian, Commented Dec 28, 2012 at 13:03

Jon Skeet · Accepted Answer · 2012-12-28 12:40:36Z

5

An array just contains a number of elements. There's no concept of an array being "empty" just because each element happens to contain the default value (0, null, or whatever).

If you want a dynamically sized collection, you should use something like List<T> instead of an array.

If you want to detect whether any element of a collection (whether that's a list, an array or anything else) is a non-default value, you have to do that via looping. (You don't have to loop in your source code, but there'll be looping involved somewhere...)

answered Dec 28, 2012 at 12:40

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Masoud Darvishian Over a year ago

i mean, in this situation that between names[0] and names[4] just names[2] is null, how can i detect that this array has one null cell?

Tony Hopkinson Over a year ago

@MesutDarvishian, you have to test each one until you run into null, not null, all not null, or all null. Only other way, would be to hide the array inside an other object, and set some flags as subitems are assigned, have to be special circumstances where that would pay off though.

Jon Skeet Over a year ago

@MesutDarvishian: I'd use LINQ: int nullElements = array.Count(x => x == null);.

Avishek · Accepted Answer · 2012-12-28 13:24:49Z

2

There is no other way than looping through, even LINQ also does the looping automatically. Instead, use a list<> and check if (listName!=null && listName.Length!=0)

Hope it helps :)

edited Dec 28, 2012 at 13:24

answered Dec 28, 2012 at 12:47

Avishek

1,89615 silver badges33 bronze badges

Comments

VoidMain · Accepted Answer · 2012-12-28 12:40:44Z

0

You can use LINQ for that, to check if any element is empty in the array you just can do:

var hasNulls = myArray.Any( a => a == null );

Or if you want to select the ones with values:

var notNulls = myArray.Where( a => a != null );

answered Dec 28, 2012 at 12:40

VoidMain

2,04721 silver badges22 bronze badges

1 Comment

Raymond Chen Over a year ago

Note that there is still a loop here. It's just that the loop is in the LINQ library instead of in the app code. (Also, you need to use default(T) so the code will work for arrays of value type, such as int[].)

Collectives™ on Stack Overflow

Detecting an empty array without looping

3 Answers 3

3 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related