Microsoft Philippines Community

We're all familiar with creating stronly-typed collection in .NET 1.1 and the MyItemCollection class below demonstrates this:

public class MyItemCollection : CollectionBase
{
    public int Add(MyItem myItem)
    {
        return List.Add(myItem);
    }
 
    public void Remove(MyItem myItem)
    {
        List.Remove(myItem);
    }

    public void Insert(int index, MyItem myItem)
    {
        List.Insert(index, myItem);
    }

    public int IndexOf(MyItem myItem)
    {
        return List.IndexOf(myItem);
    }
 
    public bool Contains(MyItem myItem)
    {
        return List.Contains(myItem);
    }

    public MyItem this[int index]
    {
        get { return List[index] as MyItem; }
        set { List[index] = value; }
    }
}

The said collection is still not strongly-typed, anybody who knows how I can add a non-MyItem type (and non-MyItem subtype) instance to a MyItemCollection instance?

by passing a generic object

MyItemCollection  myItems = new MyTemCollection();
myItems.Add ((object) "string item not a my item");

you'll be issued a compile error with that...

sorry on top of my head solution kse .. anyhow no restriction ba or inherit the collection and hide or shadow the add method to accept non-MyItems.. although that is cheating already,,

by inheriting from it, you'll not be adding to MyItemCollection instance but from its subclass instance...

Ok clarification when you mean MyItem sub-type all those non MyItem object and their descendant? Coz the other way around is to inherit from MyItem and the descendant is technically no longer the same as with the base class, except for its inherited members/properties.

sub-type = subclass = descendant

obviously you can add a MyItem subtype instance since it will be boxed as a MyItem type.

hmmm.

bonskijr wrote:

by passing a generic object MyItemCollection  myItems = new MyTemCollection(); myItems.Add ((object) "string item not a my item");

How about typecasting the Collectionbase to IList interface:
((IList)myItems).Add("Not MyItem Type");
((IList)myItems).Add(new Object());
((IList)myItems).Add(new OtherType());

bonskijr wrote:

bonskijr wrote: by passing a generic object MyItemCollection  myItems = new MyTemCollection(); myItems.Add ((object) "string item not a my item"); How about typecasting the Collectionbase to IList interface: ((IList)myItems).Add("Not MyItem Type"); ((IList)myItems).Add(new Object()); ((IList)myItems).Add(new OtherType());

good job!  di mo na pinagbigyan iba ah...  so in order to prevent this, you'd have to override OnValidate.  For more info see my blog post here.