Thee Web Part we talk about here derived from System.Web.UI.WebControls.WebParts.
using System;
    using System.Web.UI;
    using System.Web.UI.WebControls.WebParts;
    using System.Xml.Serialization;
    namespace LitwareWebPartsLab2
    {
    public class RevenueWebPart:WebPart
 {
    private bool _myBool = false;
protected override void RenderContents(HtmlTextWriter writer)
 {
     if (_myBool)
     writer.Write("<B>Hello, world</B>");
     else
     writer.Write("Hello, world");
    }
[Personalizable(PersonalizationScope.Shared),
 WebBrowsable(true),
     System.ComponentModel.Category("Miscellaneous"),
     WebDisplayName("Show Text As Bold"),
     WebDescription("Show Text As Bold.")]
     // The accessor for this property.
    public bool showTextAsBold
 {
    get
 {
     return _myBool;
    }
set
 {
     _myBool = value;
    }
}
}
}