// Derive the CustomHyperLinkDesigner from the HyperLinkDesigner.
public class CustomHyperLinkDesigner : HyperLinkDesigner
{
    // Override the GetDesignTimeHtml to set the CustomHyperLink Text 
    // property so that it displays at design time.
    public override string GetDesignTimeHtml()
    {
        CustomHyperLink hype = (CustomHyperLink)Component;
        string designTimeMarkup = null;

        // Save the original Text and note if it is empty.
        string text = hype.Text;
        bool noText = (text.Trim().Length == 0);

        try
        {
            // If the Text is empty, supply a default value.
            if (noText)
                hype.Text = "Click here.";

            // Call the base method to generate the markup.
            designTimeMarkup = base.GetDesignTimeHtml();
        }
        catch (Exception ex)
        {
            // If an error occurs, generate the markup for an error message.
            designTimeMarkup = GetErrorDesignTimeHtml(ex);
        }
        finally
        {
            // Restore the original value of the Text, if necessary.
            if (noText)
                hype.Text = text;
        }

        // If the markup is empty, generate the markup for a placeholder.
        if(designTimeMarkup == null || designTimeMarkup.Length == 0)
            designTimeMarkup = GetEmptyDesignTimeHtml();

        return designTimeMarkup;
    } // GetDesignTimeHtml
} // CustomHyperLinkDesigner

//引入命名空间
using System.Web;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.Security.Permissions;

namespace Examples.CS.WebControls.Design
{
    // The CustomHyperLink is a copy of the HyperLink.
    // It uses the CustomHyperLinkDesigner for design-time support. 
    [AspNetHostingPermission(SecurityAction.Demand, 
        Level = AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, 
        Level = AspNetHostingPermissionLevel.Minimal)]
    [Designer(typeof(Examples.CS.WebControls.Design.
        CustomHyperLinkDesigner))]
    public class CustomHyperLink : HyperLink
    {
    } // CustomHyperLink
} // Examples.CS.WebControls.Design