I would like to add an operator to a class. I currently have a GetValue() method that I would like to replace with an [] operator.
class A
{
private List<int> values = new List<int>();
public int GetValue(int index) => values[index];
}
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4 Answers
public int this[int key]
{
get => GetValue(key);
set => SetValue(key, value);
}
5 Comments
dso
Why is it that every time I need to implement an index operator, I have to look it up? And each time I end up on this answer... wish I could vote it up multiple times :)
Michael come lately
This is so super awesome. Can it be done in an interface?
interface ICache { object this[string key] { get; set; } } Edit: Yes.
JonnyRaa
dont know why they chose to omit the word 'operator' in this declaration - thats the mistake I always make! Nice answer
Colin Emonds
Michael: You should probably be using generics:
interface ICache<TContent> { TContent this[string key] { get; set; } }.
Paul Baxter
You can also use multi dimensional array
public int this[int x, int y]I believe this is what you are looking for:
Indexers (C# Programming Guide)
class SampleCollection<T>
{
private T[] arr = new T[100];
public T this[int i]
{
get => arr[i];
set => arr[i] = value;
}
}
// This class shows how client code uses the indexer
class Program
{
static void Main(string[] args)
{
SampleCollection<string> stringCollection =
new SampleCollection<string>();
stringCollection[0] = "Hello, World";
System.Console.WriteLine(stringCollection[0]);
}
}
Comments
The [] operator is called an indexer. You can provide indexers that take an integer, a string, or any other type you want to use as a key. The syntax is straightforward, following the same principles as property accessors.
For example, in your case where an int is the key or index:
public int this[int index]
{
get => GetValue(index);
}
You can also add a set accessor so that the indexer becomes read and write rather than just read-only.
public int this[int index]
{
get => GetValue(index);
set => SetValue(index, value);
}
If you want to index using a different type, you just change the signature of the indexer.
public int this[string index]
...
1 Comment
DrPhill
And don't forget you can have any combination of types for multiple indexers....
public int this[int index]
{
get => values[index];
}
