v2 :

namespace DevWebPartLivre
{
    /// <summary>
    /// Description for WPHello.
    /// </summary>
    [DefaultProperty("Text"),
    ToolboxData("<{0}:WPHello runat=server></{0}:WPHello>"),
    XmlRoot(Namespace="DevWebPartLivre")]
  public class WPHello : Microsoft.SharePoint.WebPartPages.WebPart
    { …
    }
}

Dans l’environnement WSS v3 et MOSS 2007, l’espace de nommage utilisé pour le développement de composant WebPart est System.Web.UI. WebControls.WebParts.WebPart. Voici un exemple de code de WebPart sous WSS v3 :

using System;
using System.Runtime.InteropServices;
using System.Web.UI;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Serialization;

using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.WebPartPages;

namespace WPDemo
{
    [Guid("b37370d2-2d19-4919-abb3-25a65036675e")]
    public class WPDemonstration : System.Web.UI.WebControls.WebParts.WebPart
    {
        protected override void Render(HtmlTextWriter writer)
        {
             // TODO: add custom rendering code here.
            // writer.Write("Output HTML");
       }
    }
}