Question

Assuming server control of type A has a protected member M, then we are also able to access A.M via declaring control tag A on some aspx page:

<asp:A runat=”server” M=”someValue” … />

But isn’t one of the rules in C# that protected members of class A can only be accessed from A and from classes derived from A? So doesn’t the ability to access member A.M via <asp:A M=”someValue” … /> syntax violate this rule, since we are basically accessing A.M from a class ( which is automatically generated aspx class ) not derived from A?!

Answer 1

Your markup cannot touch a protected property. I just tested this:

<cc1:ServerControl1 ID="ServerControl11" runat="server" Text="Text Set"
     ProtectedText="foo" />

protected string ProtectedText { get; set; }

protected override void RenderContents(HtmlTextWriter output)
{
    output.Write(Text);
    output.Write(ProtectedText);
}

This does not display “foo”. The property is never modified.

If you set the page to Debug=”true”:

<%@ Page Language="C#" ... Debug="true" %>

then the C# files that ASP.NET turns your markup into will be left on disk under C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files. It will take some hunting to find the right directory, but here’s what I saw for that markup:

[System.Diagnostics.DebuggerNonUserCodeAttribute()]
private global::ServerControl1.ServerControl1 @__BuildControlServerControl11() {
    global::ServerControl1.ServerControl1 @__ctrl;

    #line 15 "C:\Documents and Settings\jsaunder\My Documents\Visual Studio 2008\Projects\SOSoln\WebApplication1\Default.aspx"
    @__ctrl = new global::ServerControl1.ServerControl1();

    #line default
    #line hidden
    this.ServerControl11 = @__ctrl;
    @__ctrl.ApplyStyleSheetSkin(this);

    #line 15 "C:\Documents and Settings\jsaunder\My Documents\Visual Studio 2008\Projects\SOSoln\WebApplication1\Default.aspx"
    @__ctrl.ID = "ServerControl11";

    #line default
    #line hidden

    #line 15 "C:\Documents and Settings\jsaunder\My Documents\Visual Studio 2008\Projects\SOSoln\WebApplication1\Default.aspx"
    @__ctrl.Text = "Text Set";

    #line default
    #line hidden

    #line 15 "C:\Documents and Settings\jsaunder\My Documents\Visual Studio 2008\Projects\SOSoln\WebApplication1\Default.aspx"
    ((System.Web.UI.IAttributeAccessor)(@__ctrl)).SetAttribute("ProtectedText", "foo");

    #line default
    #line hidden
    return @__ctrl;
}

Note what happened to my “foo”.