some question about try it out on page 227

zedjr · August 15th, 2011, 08:33 AM

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class MasterPages_Frontend : System.Web.UI.MasterPage
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string selectedTheme = Page.Theme;
HttpCookie preferredTheme = Request.Cookies.Get("PreferredTheme");
if (preferredTheme != null)
{
selectedTheme = preferredTheme.Value;
}
if (!string.IsNullOrEmpty(selectedTheme) && ThemeList.Items.FindByValue(selectedTheme) != null)
{
ThemeList.Items.FindByValue(selectedTheme).Selecte d = true;
}
}
}
protected void ThemeList_SelectedIndexChanged(object sender, EventArgs e)
{
HttpCookie preferredTheme = new HttpCookie("PreferredTheme");
preferredTheme.Expires = DateTime.Now.AddMonths(3);
preferredTheme.Value = ThemeList.SelectedValue;
Response.Cookies.Add(preferredTheme);
Response.Redirect(Request.Url.ToString());
}
}

1. if (!Page.IsPostBack) pagepostback returns true if these is a current postback going on right? so if true this dont get executed. the not operator always confuses me for some reason.
2. string selectedTheme = Page.Theme; where does the page object come from

3.HttpCookie preferredTheme = Request.Cookies.Get("PreferredTheme"); "PreferredTheme" I assume this iscome from the selected index part where it assigns a name variable to the object preferred theme. Right
4. the rest of the code i am confused also. Will post mny other questions once i understand this first part.

Imar · August 15th, 2011, 08:48 AM

Hi there,

1) Yes. It fires when the page loads the first time, which means there's no postback. This code is functionally equivalent to:

if (Page.IsPostBack == false)

2) It's a property on the Page class itself (the one in which this code executes): http://msdn.microsoft.com/en-us/libr...trol.page.aspx

3.
>> I assume this iscome from the selected index part where it assigns a name variable to the object preferred theme

Not sure I understand this question. The cookies collection is an indexed collection where you can retrieve cookies by their name. PreferredTheme in this case is the name of the cookie that the code looks for. If there's a cookie by that name it's returned, otherwise the Get method returns null.

Cheers,

Imar

zedjr · August 15th, 2011, 09:34 AM

HttpCookie preferredTheme = Request.Cookies.Get("PreferredTheme");
request.cookies.get is a static method. IS this right? ANd it is returning what?
i am assuming it is returning the object made from the selected index function. which is stored on your hard drive in the interenet cookie section right. AND then it is putting the name "preferredtheme" into the httpcookie object preferred theme.

so page is a static class. or is it some sort of asp.net thing. i guess i will read mroe about this later.

Imar · August 15th, 2011, 10:01 AM

Quote:

request.cookies.get is a static method. IS this right? ANd it is returning what?

No, it's not. It's a collection property (not a method) on an *instance* of the Page class. If it were static, all users in your system would share the same cookies ;-) The type of the collection is HttpCookieCollection. You can read more about cookies in ASP.NET here:

http://msdn.microsoft.com/en-us/libr...t.cookies.aspx
http://msdn.microsoft.com/en-us/library/ms178194.aspx

Quote:

i am assuming it is returning the object made from the selected index function. which is stored on your hard drive in the interenet cookie section right. AND then it is putting the name "preferredtheme" into the httpcookie object preferred theme.

Yeah, sort of. It's a collection filled by ASP.NET for each request based on the cookies that the browser submits. Each item in the collection is an HttpCookie that contains data you as a developer have assigned to it (as well as other cookies that may have been set for the domain). In the SelectedIndexChanged method of the Master Page you created an HttpCookie, added it the *Response.Cookies* collection using PreferredTheme as the key which in turn caused the cookie to be sent to the client. Then on each new request that cookie is sent back to the server where it's available in the Request.Cookies collection.

Quote:

so page is a static class

No, it's not. or all users would be sharing the same page. Each request for an ASPX page results in a new instance of the Page class being created. The code you write in the code behind then works against that instance.

Hope this helps,

Imar