C#: Fun with Indexers

This post refers to an interesting situation when you create a class in C# with an indexer and a property named “Item”. Let’s see why this is not possible simultaneously.

Few days back, I got an interesting error. I had a class with a property named Item and an indexer like this:

public class SomeClass
{
    List<int> someList;

    //property
    public string Item { get; set; }
        
    //indexer
    public int this[int index]
    {
        get { return someList[index]; }
        set { someList[index] = value; }
    }
}

Nothing special? But when I tried to compile, it complained saying:

The type 'MyNamespace.DataClasses.SomeClass' already contains a definition for 'Item'.

Strange!! and the location of the error as pointed by Visual Studio was my indexer:

Well, the reason is that internally, C# converts the indexer to a property name ‘Item’ to be able to support other languages that don’t directly support indexers. Since I had already defined a property name Item, so a conflict was created. Luckily, this can be solved by forcing the compiler to use a custom name other than ‘Item’ by using the IndexerNameAttribute. So, here’s a quick fix for such situation:

[IndexerName("Indexer")]
public int this[int index]
{
    get { return someList[index]; }
    set { someList[index] = value; }
}

Enjoy!!!

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