Question

I am working on a filtering function. The filter will be an expression tree build by an user. There will be about 30 fields the user can use for filtering. I think the best way is to create the object model with indexer and to access required values by index of enum type.

See this example:

enum Field
{
    Name,
    Date,
}

class ObjectModel
{
    object this[Field Key]
    {
        get 
        {
            //...
            return xx;
        }
    }
}

I would like to ask how can I access an indexer from an expression tree.

Answer 1

The indexer is a simple property, normally called Item. This means, you can access the indexer like any other property by using its name.

The name of the indexer property can be changed by the implementor of the class by means of the IndexerName attribute.

To reliably get the actual name of the indexer property, you have to reflect on the class and obtain the DefaultMember attribute.
More information can be found here.