Basic C# class question regarding the "this" keyword

Question

I'm going through someone else's code and I saw this statement:

public CustomClassName this [ string varName]

Please excuse the newbness of this question, but the square brackets threw me off. Is this a method or constructor?

How does the "this" variable work in this case?

score 6 · Accepted Answer · answered Sep 15 '11 at 18:42

6

It's called an indexer. MSDN page.

answered Sep 15 '11 at 18:42

Bala R

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So that's how it's done! VB.NET's `Default` is a lot more clear :) – Ry- Sep 15 '11 at 18:43
@minitech: Highly debatable. I haven't come across a single construct in VB that I thought was more clear than it's C# allegory. – Ed S. Sep 15 '11 at 18:45

score 1 · Answer 2 · answered Sep 15 '11 at 18:44

1

Neither, it's an Indexer. It allows you to do CustomClassName[ obj ] and retrieve a value from the object.

answered Sep 15 '11 at 18:44

Brandon Moretz

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score 0 · Answer 3 · answered Sep 15 '11 at 18:43

0

It is an indexer, so you can access the class similar to an array.

answered Sep 15 '11 at 18:43

tcarvin

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score 0 · Answer 4 · answered Sep 15 '11 at 18:43

It is defining an index operator on your type. Take for example, the List<T> class. The library designers wanted you to be able to write code like this:

List<int> list = new List<int> { 1, 2, 3, 4, 5 };
int x = list[2]; // x == 3

The syntax that accomplishes that is what you have posted above. So, for your own types, you can...

class NameCollection : /* whatever */
{
    private List<string> _names = new List<string> { "Ed", "Sally", "John" };

    public string this[int index]
    {
        get { return _names[index]; }
    }
}

score 0 · Answer 5 · edited May 23 '17 at 10:24

0

this is simply an overload of the square-bracket operator in C#.

see here:

How do I overload the square-bracket operator in C#?

edited May 23 '17 at 10:24

Community

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answered Sep 15 '11 at 18:43

Davide Piras

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Basic C# class question regarding the "this" keyword

5 Answers5