Question

In Delphi you can do something like this :

TArray = array[1..3] of byte;

where you can then declare

T2Array = array[1..3] of TArray

ad nauseum…

Does something like this exist in .NET? (vb, c#, whatever)

I am currently doing something like this

Private LotsOfData As ObservableCollection(Of ObservableCollection(Of myClass))

but would like to do

Private LotsOfData As ObservableCollection(Of myType)

where

myType -->  ObservableCollection(Of myClass)

I know you can do this with structures, ie:

Public Structure MyType
     Public myOc as ObservableCollection(Of MyClass)
End Structure

Dim LotsOfData as ObservableCollection(of MyType)

but you then have to reference it as (for example)

LotsOfData.Last.myOc(i) 

instead of

LotsOfData.Last(i)

which seems clumsy. This also seems clumsy :

For Each Data as ObservableCollection(of myClass) in LotsOfData
     DoSomething(Data)
Next

as does

For Each Data as MyType in LotsOfData
     DoSomething(Data.myOc)
Next

when it could be

For Each Data as MyType in LotsOfData
     DoSomething(Data)
Next

Any ideas?

Answer 1

How about defining custom classes that derive from the closed type of your generic collection? For example:

public class MyType : ObservableCollection<MyClass>
{ }

Then you could create another generic collection whose type parameter is your above-defined class (which is itself a collection):

ObservableCollection<MyType> lotsOfData = new ObservableCollection<MyType>();

When you iterate over it, you would get the sequence of inner collections:

foreach (ObservableCollection<MyClass> data in lotsOfData)
{
    DoSomething(data);
}

Edit: Deriving as shown above will allow you to inherit all accessible members from the base ObservableCollection<T> class, but you won’t be able to call its (non-default) constructors. Thus, you would typically want to implement the constructors with the same overloads as the base class:

public class MyType : ObservableCollection<MyClass>
{
    public MyType()
        : base()
    { }

    public MyType(IEnumerable<MyClass> collection)
        : base(collection)
    { }

    public MyType(List<MyClass> list)
        : base(list)
    { }
}