Array property syntax in C#

Question

I have a a class that has an integer array property and I am trying to figure out the right syntax for it. The integer array gets instantiated in the class constructor.

class DemoClass
{
    private int[] myNumbers;
    public int[] MyNumbers
    {
        get { /* Some logic */ }
        set { /* Some logic */ }
    }

    public DemoClass(int elements)
    {
        // Here, the array should get instantiated using the elements.
    }
}

How does the get/set block syntax work if I want my client code to retrieve a number from the array through the property MyNumbers?
How can I send it the right index?
What do I have to initialize?

Are you trying to create an indexer property by any chance?

Serguei
– Serguei

2011-08-11 19:00:43 +00:00
Commented Aug 11, 2011 at 19:00 — Serguei
– Serguei, Commented Aug 11, 2011 at 19:00

Blindy · Accepted Answer · 2016-04-25 22:05:47Z

27

Are you looking for:

class DemoClass
{
    public int[] MyNumbers { get; private set; }

    public DemoClass(int elements)
    {
        MyNumbers = new int[elements];
    }
}

As for normal properties that do nothing except publicize a private field (as you seem to want):

private int[] myNumbers;
public int[] MyNumbers
{
    get { return myNumbers; }
    set { myNumbers = value; }
}

edited Apr 25, 2016 at 22:05

answered Aug 11, 2011 at 18:59

Blindy

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6 Comments

Gasoline Over a year ago

I would like to know how it works when I am not using automatic properties and have a field for storing the array.

Serguei Over a year ago

Arrays are just a reference type in C# you can cast int[] to System.Array` for instance. Without auto-properties you just do int[] nums; public int[] Nums { get { return nums;} set { nums = value } }. Mind you if you want to get/set individual elements of the array you need to make an indexer property.

Joel Coehoorn Over a year ago

I would suggest also using a private setter.

Gasoline Over a year ago

Thanks, it works! I think I overthought it by thinking how the right index is passed to the MyNumbers property but it was done automaticly. Still lot to learn. Also thank you Serguei. I will look into index properties and see what they can do.

user4593252 Over a year ago

It should be noted that Microsoft does not recommend using arrays in properties: msdn.microsoft.com/en-us/library/0fss9skc%28v=vs.120%29.aspx

|

Derek Johnson · Accepted Answer · 2013-08-25 11:51:05Z

17

CA1819: Properties should not return arrays

http://msdn.microsoft.com/en-us/library/0fss9skc.aspx

Arrays returned by properties are not write-protected, even if the property is read-only. To keep the array tamper-proof, the property must return a copy of the array. Typically, users will not understand the adverse performance implications of calling such a property. Specifically, they might use the property as an indexed property.

To fix a violation of this rule, either make the property a method or change the property to return a collection instead of an array

answered Aug 25, 2013 at 11:51

Derek Johnson

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Comments

Joel Coehoorn · Accepted Answer · 2011-08-11 19:00:01Z

1

If the number of element in the array is fixed, I would only provide a getter for the array and leave off the setter. You will still be able to assign values to individual elements in the array, but this will prevent someone from swapping the whole array out from under you (or setting it to null. The code would look like this:

class DemoClass
{
    public int[] MyNumbers
    { get; private set; }

    public DemoClass(int elements)
    {
        MyNumbers = new int[elements];
    }
}

If the number of elements are not fixed, then you should use a List<int> rather than an array, and then you definitely want a property with no setter.

answered Aug 11, 2011 at 19:00

Joel Coehoorn

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Comments

Haris Hasan · Accepted Answer · 2011-08-11 19:00:12Z

0

 class DemoClass
    {
        private int[] myNumbers;
        public int[] MyNumbers
        {
            get { return myNumbers; }
            set { myNumbers = value; }
        }

        public DemoClass(int[] elements)
        {
            myNumbers = elements;
            // Here, the array should get instantiated using the elements.
        }
    }

answered Aug 11, 2011 at 19:00

Haris Hasan

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Comments

Vlad Bezden · Accepted Answer · 2011-08-11 19:06:04Z

0

It is called Auto-Implemented Properties . So if you have syntax like

public int[] MyNumbers { get; set; }

C# compiler will automatically create for you backing field. This feature was introduced in C# 3.0, and before that you always had to implement property with backing field.

You can read more at: New C# "Orcas" Language Features: Automatic Properties, Object Initializers, and Collection Initializers

answered Aug 11, 2011 at 19:06

Vlad Bezden

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Comments

Dylan Meador · Accepted Answer · 2011-08-11 19:00:47Z

-2

class DemoClass
{
    private int[] myNumbers;
    public int[] MyNumbers
    {
        get { return myNumbers; }
        set { myNumbers = value;}
    }

    public DemoClass(int elements)
    {
        // Here, the array should get instantiated using the elements.
        MyNumbers = new int[5] { 1, 2, 3, 4, 5};
    }
}

answered Aug 11, 2011 at 19:00

Dylan Meador

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