Sortable CollectionBase ?

[Gavin Roberts]

Hi all, I'm working on an application, and being new to 2.0 I need some help. I have a Custom Collection which inherits CollectionBase and i'm using this as a DataGridView datasource. All is fine, apart from the Sorting does not work anymore (I used to manually add each row.) When I tried to use Sort, it complained that my CollectionBase does not inherit the IBindingList class. I've tried but I never really got far. Does anyone have any examples which will help me? using System; using System.Collections; using System.Windows.Forms; using System.Text; using System.ComponentModel; namespace HelpDesk { class RequestCollection : CollectionBase { public void Add(Request r) { r.Parent = this; List.Add(r); } public Request this[int index] { get { return (Request)List[index]; } set { List[index] = value; } } private ImageList _Images; public ImageList Images { get { return _Images; } set { _Images = value; } } public int OpenCount { get { int ReturnValue = 0; foreach (Request r in List) { if (r.Status == RequestStatus.Open) ReturnValue++; } return ReturnValue; } } public int PendingCount { get { int ReturnValue = 0; foreach (Request r in List) { if (r.Status == RequestStatus.Pending) ReturnValue++; } return ReturnValue; } } public int ImmediateCount { get { int ReturnValue = 0; foreach (Request r in List) { if (r.Priority == RequestPriority.Immediate) ReturnValue++; } return ReturnValue; } } public int HighCount { get { int ReturnValue = 0; foreach (Request r in List) { if (r.Priority == RequestPriority.High) ReturnValue++; } return ReturnValue; }

[Pete OHanlon]

You may want to use a generic list instead. This article[^] shows you how to add a generic sort routine.

Deja View - the feeling that you've seen this post before.

[Martin 0]

Hello, I think you have to call the Sort method of the InnerList property. There you have to pass an instance of a UserComparer class inheritet from IComparer. For excample, if your Request class has a Name property which you whant to use for sorting:

public class YourComparer : IComparer  
{
	int IComparer.Compare( object x, object y )  
	{
		Request  request\_x= x as Request ;
		Request  request\_y= y as Request ;
		if((request\_x!=null)&&(request\_y!=null))
		{
			return( (new CaseInsensitiveComparer()).Compare( request\_x.Name, request\_y.Name ) );
		}
		else
		{
			return 0;
		}
	}
}

Hope it helps! All the best, Martin

[Gavin Roberts]

Hmm, This annoys me about .Net 2.0. I want a collection dedicated to one type, and they bring out generic collections?! Probably why i've not hit that part of .Net 2.0 just yet. I've tried the following http://en.csharp-online.net/Understanding_Generics%E2%80%94Creating_a_Custom_Generic_Collection[^] but received errors. I need to be able to have methods and custom properties for my collection, if there is a way to do this, i'd be greatful if you could let me know. Thanks

[Pete OHanlon]

I use List<...> for a lot of code. I find it convenient to be able to have a wrapped list. Here's an example with a simple method to demonstrate how easy it is:

using System.Collections.Generic;
using System;

namespace Generics.Test
{
  public class TestGeneric
  {
    public TestGeneric()
    {
      MyList<MyTest> test = new MyList<MyTest>();
      test.Add(new MyTest("Test 1"));
      test.Add(new MyTest("Test 2"));
      if (test.HasValue("Test 2"))
        Console.WriteLine("Test 2 is present");
    }
  }

  public interface ISomeValue
  {
    string SomeValue { get; set; }
  }
  public class MyList<T> : List<T>, IEnumerable<T> where T : ISomeValue
  {
    public bool HasValue(string key)
    {
      foreach (T item in this)
      {
        if (item != null && item.SomeValue == key)
            return true;
      }
      return false;
    }

    #region IEnumerable<T> Members

    IEnumerator<T> IEnumerable<T>.GetEnumerator()
    {
       for (int i = 0; i < this.Count; i++)
       {
          yield return this[i];
       }
    }

    #endregion

    #region IEnumerable Members

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
      throw new Exception("The method or operation is not implemented.");
    }

    #endregion
  }
}

Deja View - the feeling that you've seen this post before.

[Gavin Roberts]

Hi there, Thanks for the sample code. I've gone to use it this morning and hit another problem. I've created this: public interface RequestCollectionInterface { ImageList Images { get; set; } int OpenCount { get; } int PendingCount { get; } int ImmediateCount { get; } int HighCount { get; } } public class RequestCollection<T> : List<T>, IEnumerable<T> where T : RequestCollectionInterface { IEnumerator<T> IEnumerable<T>.GetEnumerator() { for (int i = 0; i < this.Count; i++) { yield return this[i]; } } IEnumerator IEnumerable.GetEnumerator() { throw new Exception("The method or operation is not implemented."); } public int OpenCount { get { int ReturnValue = 0; foreach (Request item in this) { if (item.Status == RequestStatus.Open) ReturnValue++; } return ReturnValue; } } public int PendingCount { get { int ReturnValue = 0; foreach (Request item in this) { if (item.Status == RequestStatus.Pending) ReturnValue++; } return ReturnValue; } } public int ImmediateCount { get { int ReturnValue = 0; foreach (Request item in this) { if (item.Priority = RequestPriority.Immediate) ReturnValue++; } return ReturnValue; } } public int HighCount { get { int ReturnValue = 0; foreach (Request item in this) { if (item.Priority = RequestPriority.High) ReturnValue++; } return ReturnValue; } } } And tried using it like this: private RequestCollection<Request> __GetRequests() { RequestCollection<Request> rc = new RequestCollection<Request>();

[Pete OHanlon]

You've become slightly mixed up in what you need the interface to be. When a generic states where T : ... you are indicating that the type T will implement the interface. Also, you have used a generic list and then hardcoded the type in the iterator. To be honest, you possibly don't need to expose your class as generic because you have a specific non-generic need here. What you could do is declare a List<...> member as a private member and then use your own methods to add to it. If you definitely want to go the generic route here, this is a sample that I have just knocked up.

using System;
using System.Collections.Generic;
using System.Text;

namespace TestIterator
{
  class Program
  {
    static void Main(string[] args)
    {
      RequestItemCollection<Request> coll = new RequestItemCollection<Request>();
      Request req = new Request();
      req.Status = RequestStatus.Open;
      coll.Add(req);
      req = new Request();
      req.Status = RequestStatus.Open;
      coll.Add(req);
      System.Console.WriteLine("Open count = {0}", coll.OpenCount);
      Console.ReadLine();
    }
  }

  public class RequestItemCollection<T> : List<T>, IEnumerable<T> where T: IStatus
  {
    #region IEnumerable<T> Members

    IEnumerator<T> IEnumerable<T>.GetEnumerator()
    {
      for (int i = 0; i < this.Count; i++)
        yield return this[i];
    }

    #endregion

    #region IEnumerable Members

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
      throw new Exception("The method or operation is not implemented.");
    }

    #endregion

    public int OpenCount
    {
      get
      {
        return StatusCount(RequestStatus.Open);
      }
    }

    public int Closed
    {
      get
      {
        return StatusCount(RequestStatus.Closed);
      }
    }

    private int StatusCount(RequestStatus status)
    {
      int count = 0;

      foreach (T item in this)
      {
        if (item.Status == status)
          count++;
      }
      return count;
    }
  }

  public enum RequestStatus
  {
    Open,
    Closed,
    Pending
  }
  public interface IStatus
  {
    RequestStatus Status { get; set; }
  }

  public class Request : IStatus
  {
    private RequestStatus _status;
    #region IStatus Members

    public RequestStatus Status
    {
      get
      {
        return _status;
      }
      set
      {
        _stat