ASP.NET

[DefaultProperty("Text")]
[ToolboxData("<{0}:MyControlrunat=server></{0}:MyControl>")]
[Designer(typeof(MyControlDesigner),typeof(IDesigner))]
[ParseChildren(ChildrenAsProperties =true)]
public class MyControl: CompositeControl
{
    [Bindable(true)]
    [Category("Settings: Value")]
    [PersistenceMode(PersistenceMode.InnerProperty)]
    [EditorAttribute(typeof(ListItemsCollectionEditor), typeof(UITypeEditor))]
    [MergableProperty(false)]
    public ListItemCollection Items
    {
        get
        {
            if (ViewState["Items"] == null)
                ViewState["Items"] = new ListItemCollection();
            return (ListItemCollection)ViewState["Items"];
        }
    }
}

public class MyControlDesigner : ControlDesigner
{
    //Properties
    public override System.ComponentModel.Design.DesignerActionListCollection ActionLists
    {
        get
        {
            DesignerActionListCollection actions = new DesignerActionListCollection();
            actions.AddRange(base.ActionLists);
            actions.Add(new LabeledControlDesignerActionLists(this));
            return actions;
        }
    }
}

class MyControlDesignerActionLists: DesignerActionList
{
    private MyControlDesigner  _designer;
    private MyControl _control;

    public MyControlDesignerActionLists(MyControlDesigner designer)
        : base(designer.Component)
    {
        this._designer = designer;
        this._control = (Mycontrol)this._designer.Component;
    }

    public override DesignerActionItemCollection GetSortedActionItems()
    {
        DesignerActionItemCollection actions = new DesignerActionItemCollection();
                actions.Add(
                    new DesignerActionPropertyItem(
                        "Items",
                        "Items",
                        "Control Value Settings",
                        "Set the value."));

        }

        return actions;
    }
    public ListItemCollection Items
    {
        get
        {
            return this._control.Items;
        }
    }

    public void SetProperty(string propertyName, object value)
    {
        PropertyDescriptor property = TypeDescriptor.GetProperties(this.Component)[propertyName];
        property.SetValue(this.Component, value);
    }
}