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;
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
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).
Indexers only work with the this
keyword. See here .
The this keyword is used to define the indexers.
Just like Matt Burland and Oded said, indexers only work with this keyword, so you need to have a proxy class with the interface you need:
public class PersonSelector
{
private MyClass owner;
public PersonSelector(MyClass owner)
{
this.owner = owner;
}
public bool this[Guid personGuid]
{
get {
Person person = owner.GetPersonByGuid(personGuid);
return person.IsSelected;
}
set {
Person person = owner.GetPersonByGuid(personGuid);
person.IsSelected = value;
}
}
}
public class MyClass
{
public MyClass()
{
this.IsSelected = new PersonSelector(this);
}
public PersonSelector IsSelected { get; private set; }
...
}
@Jojan answered here :
C# 3.0 spec
"Overloading of indexers permits a class, struct, or interface to declare multiple indexers, provided their signatures are unique within that class, struct, or interface."
or if your data set is small you can IList
public IList<Boolean> IsSelected
{
get { ... }
}
public IList<Boolean> IsApproved
{
get { .... }
}
Actually you can have multiple indexers accepting types.
However you can not have two indexers with the same signature. Same signature means the parameter number and types - so the above code has two indexers with same signature.
If the code changed to :
Boolean this[string x, Guid personguid]
and :
Boolean this[Guid personguid]
it should work.
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