Multiple Indexers in C#

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2022-07-28

In C#, you can't have multiple indexers like you can do in VB, so the following code is not supported:
 

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class C
{
public Foo Foos[int i]
{
...
}
public Bar Bars[int

 
On the other hand, exposing internal ​​​IEnumerable ​​​is not always a desired solution (because you want to limit access to your internal collections - that's why indexers are for in the first place.)
 

Workaround

 
I came up with this simple class that you can add to your code:
 

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public class IndexProperty<T,I>
{
private Func<I,T> getter;
private Action<I, T> setter;

public IndexProperty(Func<I, T> g, Action<I, T> s)
{
if (g == null || s == null)
throw new ArgumentNullException();
getter = g;
setter = s;
}

public T this[I index]
{
get
{
return getter(index);
}
set

 
Now, you can add multiple indexers to your class, but make sure you initialize the indexers properly. The following example demonstrates how to expose multiple indexers:
 

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public class MyClass
{
private List<string> myList = new List<string>();
public MyClass()
{
myList.AddRange(new string[]{"1","2","3"});
// Init the IndexProperty with your methods (or lambdas)
this.Keys=new IndexProperty<string,int>(
i=> myList[i],
(j,val)=> myList[j]=val);
}

public IndexProperty<string,int> Keys { get; set; }
}

 
The following code demonstrates how your class can be used:
 

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static void SampleMethod()
{
MyClass c = new MyClass();
c.Keys[0] = "value";
}

欢迎沟通及共同进步

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