Non-integer indexed Indexer properties in C#

Question

I want to have an indexed property in C#:

public Boolean IsSelected[Guid personGuid]
{
   get {
      Person person = GetPersonByGuid(personGuid);
      return person.IsSelected;
   }
   set {
      Person person = GetPersonByGuid(personGuid);
      person.IsSelected = value;
   }
}
public Boolean IsApproved[Guid personGuid]
{
   get {
      Person person = GetPersonByGuid(personGuid);
      return person.IsApproved;
   }
   set {
      Person person = GetPersonByGuid(personGuid);
      person.IsApproved= value;
   }
}

Visual Studio complains on the non-integer indexer syntax:

i know .NET supports non-Integer indexors.

---

In another language i would write:

private
   function GetIsSelected(ApproverGUID: TGUID): Boolean;
   procedure SetIsSelected(ApproverGUID: TGUID; Value: Boolean);
   function GetIsApproved(ApproverGUID: TGUID): Boolean;
   procedure SetIsApproved(ApproverGUID: TGUID; Value: Boolean);
public
   property IsSelected[ApproverGuid: TGUID]:Boolean read GetIsSelected write SetIsSelected;
   property IsApproved[ApproverGuid: TGUID]:Boolean read GetIsApproved write SetIsApproved;
end;

Answer 1

Your syntax is incorrect:

public Boolean this[Guid personGuid]
{
   get {
      Person person = GetPersonByGuid(personGuid);
      return person.IsSelected;
   }
   set {
      Person person = GetPersonByGuid(personGuid);
      person.IsSelected = value;
   }
}

Indexers are declared using the this keyword - you can't use your own name.

From Using Indexers (C# Programming Guide):

To declare an indexer on a class or struct, use the this keyword

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Additionally, it is only possible to have one indexer that accepts a type - this is a limitation of the indexer syntax of C# (might be an IL limitation, not sure).