How do I sort a KeyedCollection ?

[bchirra]

Can I sort a KeyedCollection ? If so how do I do it. Please, any help on this issue is very much appreciated. Thank you.

[bchirra]

Any idea's how I can sort a KeyedCollection . Thank you.

[SammyB]

Any idea's how I can sort a KeyedCollection . Thank you.

I cannot see anyway to do this. In fact, I cannot see any way to retrieve the keys from a collection. Can you convert your Collection to a SortedDictionar y?

Dim s As New SortedDictionary(Of String, String)
s.Add("txt", "notepad.exe")
s.Add("bmp", "paint.exe")
s.Add("dib", "paint.exe")
s.Add("rtf", "wordpad.exe")
 

Notice that the key is first, not second as in collections.

[Plater]

I could not find any object called KeyedCollection .
The only collections with Keys I have seen have a .Keys proprty that returns a string[]. And that is very easy to sort.

Must sort functions (like the generic Array.Sort() ) take a custom thing to sort objects (Icomparable or something like that) in which you can define you own method to decide which comes first between two objects.

[SammyB]

I could not find any object called KeyedCollection .

You've made my day: I almost posted the same reply. I think that bchirra is using an old Collection object: remember, they could have keys:

Dim c As New Collection
c.Add("notepad.exe", "txt")
c.Add("paint.exe", "bmp")
c.Add("paint.exe", "dib")
c.Add("wordpad.exe", "rtf")
 

As you said, if you could get to the keys, sorting would be easy, but these keys seem to be write-only! I had no idea that the Collection object was still around. --Sam

[Plater]

Ahh I see it's part of the VisualBasic compatibility. (And also in System.Collecti ons.ObjectModel .KeyedCollectio n)
You could also have a second single-dimensioned array (ArrayList is good)
wherein whenever your Collection object is populated, you add the value of the KEY to that second array.
Then all you need to do is sort that array. Remember: Only the Keys need to be sorted if you reference your Collection object using the value of the Key.

I would def say time to upgrade to an actual collection object. Since KeyedColelction is abstract you must be creating a custom class that inherits KeyedCollection , at which point YOU are in charge of coding in your custum method to retrieve the key. So you are really digging your own hole on that one.

[bchirra]

Thank you for your replies.

Yes, I have a custom class that inherts from KeyedCollection which is part of
namespace: System.Collecti ons.ObjectModel (new class in .net 2.0).

Can I modify my class to inherit from generic SortedList? What is default sort order of the SortedList, Asce or Desc? Thank you.

[Plater]

You could override the add function to track the key in your own way. (Still not sure why you are using this setup to begin with)

I did this, not sure it's correct:

public class mylist : System.Collections.ObjectModel.KeyedCollection<string,int>
    {
        protected override string GetKeyForItem(int item)
        {
            int idx = base.IndexOf(item);
            foreach (string n in base.Dictionary.Keys)
            {
                if (base[n] == item)
                {
                    return n;//or something
                }
            }
            throw new Exception("The method or operation is not finished.");
        }
        public ICollection<string> Keys
        {
            get
            {
                return base.Dictionary.Keys;
            }
        }
    }
 

Thank you for your replies.

Yes, I have a custom class that inherts from KeyedCollection which is part of
namespace: System.Collecti ons.ObjectModel (new class in .net 2.0).

Can I modify my class to inherit from generic SortedList? What is default sort order of the SortedList, Asce or Desc? Thank you.

[bchirra]

Thank you very much. I will try it out.

[SammyB]

Thank you for your replies.

Yes, I have a custom class that inherts from KeyedCollection which is part of
namespace: System.Collecti ons.ObjectModel (new class in .net 2.0).

Can I modify my class to inherit from generic SortedList? What is default sort order of the SortedList, Asce or Desc? Thank you.

If you have keys and you want to sort, then I would think that you would want to use SortedDictionar y as your base class.