WebParts in asp.net
* Objective:
  To develop a web
application using WebParts in asp.net
* Design: 
->
Design the form with one WebPartManager, one DropDownList, two or more
WebPartZone controls, one CatalogZone control, one EditorZone control.
->
Create few web user controls and place one in WebPartZone1, another in WebPartZone2
->
Now place DeclarativeCatalogPart control in CatalogZone1
select DeclarativeCatalogPart1->click on '>' button, select 'Edit Templates'and place all the
created webusercontrols in it-> select 'End TemplateEditng'.
->
Place LayoutEditorPart, AppearanceEditorPart, PropertyGridEditorPart,
BehaviourEditorPart in EditorZone1
->Select
DropDownList1-> Edit Items-> Add Browse,Design,Catalog,Design
and also check EnableAutoPostBack option
 
* Code: 
using System;
using
System.Web.UI.WebControls;
using
System.Web.UI.WebControls.WebParts;
 
public partial class _Default : System.Web.UI.Page
{
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs
e)
    {
        switch
(DropDownList1.SelectedIndex)
        {
            case
0:
                WebPartManager1.DisplayMode = WebPartManager.BrowseDisplayMode;
                break;
            case
1:
                WebPartManager1.DisplayMode = WebPartManager.DesignDisplayMode;
                break;
            case
2:
                WebPartManager1.DisplayMode = WebPartManager.CatalogDisplayMode;
                break;
            case
3:
                WebPartManager1.DisplayMode = WebPartManager.EditDisplayMode;
                break;
            default:
                break;
        }
    }
}