Today I wrote a simple example which shows how we can use CollectionEditor of the .NET. In addition to this I also made a simple example which shows how to implement custom CollectionEditor which allows us to add more than one item to the collection.

An example screenshot of the Collection Editor

public class ExampleComponent : Component{	      
   ArrayListCollection _ArrayListItems = new ArrayListCollection();
   List<Button> _ListItems = new List<Button>();
   List<Control> _MultipleItems = new List<Control>();
   public ExampleComponent()
   { }
   [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
   [Description("Contains only Control objects in an ArrayList")]
   [Category("Behaviour")]
   public ArrayListCollection ArrayListItems
   {
      get { return _ArrayListItems; }
   }
   [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
   [Description("Contains only Button objects in a List collection)]
   [Category("Behaviour")]
   public List<Button> ListItems
   {
       get { return _ListItems; }
   }
			
   // custom editor attribute
   [Editor(typeof(CustomCollectionEditor), typeof(UITypeEditor))]
   [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
   [Description("Contains ListView, Button and  CheckBox items in a List collection")]
   [Category("Behaviour")]
   public List<Control> MultipleItems
   {
	get { return _MultipleItems; }
   }
			
   public class ArrayListCollection : ArrayList
   {
      // CollectionEditor searches collection type's Index property and finds its property type.
      // It uses this type to add new items
      public new Control this[int index]
      {
	 get { return base[index] as Control;
      }
   }		      
 
			
   // Custom collection editor.
   // by using this editor we can add ListView, Button and
   // CheckBoxes to the same collection
   public class CustomCollectionEditor : CollectionEditor
   {
	public CustomCollectionEditor(): base(typeof(List<Control>))
	{}
	// override this method if you have to do custom initializing
	// operations. For example, if you have to use a constructor which
	// takes arguments you can create your own items here ...
        // or may  be you have to do some initializing operations ...
        protected override object CreateInstance(Type  itemType)
       {
	   if (itemType == typeof(CheckBox))
	   {
		CheckBox checkbox = new CheckBox();
		checkbox.Text = "My Text,hede";
	        return checkbox;
			                   
	   }
	   Control control = base.CreateInstance(itemType) as Control;
	   control.Text = "Other, hede";
	   return control;
       }

       // if you want to use a custom collection editor form,
       // you have to override this method and return your form here
        protected override CollectionEditor.CollectionForm CreateCollectionForm()
       {
	   return base.CreateCollectionForm();
       }
			
       // here you can return a text which will be appeared in the list
        // for the given item
        protected override string GetDisplayText(object value)
        {
             Control control = value as Control;
             return string.Format("{0} - {1}", control.GetType().Name, control.Text);		            
        }
			
        // we allow 3 types can be added to our collection
	protected override Type[] CreateNewItemTypes()
	{
            return new Type[] 
            { 
                typeof(ListView), typeof(Button), typeof(CheckBox)};
	    }			      
        }
    }
}