Indexed properties mapping support (part of property bag entities)

[lajones]

From discussion with @divega and @ajcvickers. We would like to support Entity classes with indexers:

    public class SomeEntity
    {
        public object this[string propertyName]
        {
            get
            {
                // get value of property named propertyName
            }

            set
            {
                // set value of property named propertyName
            }
        }
    }

You can then declare an indexed property in OnModelCreating() and have EF use the indexer to access that property, instead of expecting a member. (Note: this addresses parts of issues #2968 and #9914).

[smitpatel]

Few questions:
@AndriySvyryd or @ajcvickers if there are already answers or we can discuss in design meeting to decide.

• Should there be AddIndexedProperty method on IMutableEntityType? Specifying memberInfo is bit cumbersome and if we know we are adding indexed property then we can fetch it from entityType.ClrType directly.
• Fluent API? or to be discussed later?
• Fields
  • Can indexer be field in C# (I really don't know)?
  • Current design assumes it to be always a propertyInfo.
  • Indexer properties can be configured to use backing field just like any other property.
  • Is there a need or should we support mapping indexer to a backing field dictionary which would be accessed directly?

[AndriySvyryd]

• You can add AddIndexedProperty extension method or default interface implementation as sugar if it's useful.
• .IndexedProperty<int>("Id") would be my first suggestion
• Indexers cannot be fields and can't have a backing field
• We don't need to support Dictionary properties at this point

[smitpatel]

Only fluent API is left now.
I will start with

.IndexedProperty("Id") would be my first suggestion

unless someone brings something better in new year.

[bigworld12]

will this issue be related to fixing #13084 and #2968

[ajcvickers]

@bigworld12 This issue is unrelated to the two that you mention.