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Including a Handler Response inside a Web Form

I am generating HTML in the Page Load method in more than 1 page.
All those generated HTML are the same across all pages.
I found that it's a pain to have the same codes in every page because once I need to change something, I need to change them in all pages.
Example:
I have a div in each of those page:
<div id="Questions" runat="server"></div>
In the Page Load method of each page, I generate the same HTML.
Questions.InnerHTML = "<span>...etc...</span>";
So I decided to make a page that generates those contents, then load this page inside the div of the other pages, means, if I ever need to change, I only change this page.
I created a Handler, Questions.ashx. This handler generates that HTML and sends back a response.
Now to include it, I know I can use JQUERY's .load() function, but I would like to generate those HTML from server side.
What I've tried:
Questions.InnerHTML = LoadControl("~/Handlers/Questions.ashx").ToString();
But I received this error:
Type 'Questions' does not inherit from 'System.Web.UI.UserControl'.

"LoadControl" is for "User Controls", not HTTP Handlers..
You will probably be better off creating a User Control, which is an .ascx file. This can contain HTML, ASPX controls and code behind, and can be referenced by any ASPX page.
More Info here:
http://msdn.microsoft.com/en-us/library/y6wb1a0e(v=vs.100).aspx

Access web control values

I have two pages in ASP.NET 3.5 and I need to access/read the web controls values from the first page but on the second page. The second page is being displayed with a single link, there is not a post event or something like that.
I guess I should use ViewState but it looks so complicated for this task so please let me know a better way to achieve this.
P.S I'm using C# and Visual Studio 2010

If I understand correctly you have two .aspx pages and you want one page to share information with the other page. Does the first page link to the second page?
I ask because there are a couple of approaches you could take. You could add parameters to a query string in the link to the second page with the information you are trying to send. You could also use the session to temporarily store the information.
For example:
<asp:HyperLink NavigateUrl="www.<yoursite>.com/firstpage.aspx?eggs=1&bacon=yum" Text="Awesome Site" runat="server" />
In the second page you would have this in the codebehind in the Page_Load
string eggs = Request.QueryString["eggs"];
string bacon = Request.QueryString["bacon"];
Now you have the value from page one available in page two.
Another approach might be to use the Session like so:
Page one:
Session["bacon"] = "Yum";
Page two:
string bacon = (string)Session["bacon"];
However, I would advise against overusing session to pass information between pages.

Quick & "Dirty": A session variable which holds the info to pass.
On the first page:
Session["ValueToPassToOtherControl"] = "The value";
On the second page:
var value = Session["ValueToPassToOtherControl"];
Elegant: You need to manage your state in any way (via a static manager whose function is to store and retrieve that info, but that will be also variables). Problem is HTTP is stateless. So you need to bypass this limitation via some kind of storing and retrieving of the data.
You suggested the use of ViewState but forget it, ViewState is the technique used by an ASP.NET Web page to persist changes to the state of a Web Form across postbacks which isn't what's happening on your scenario.

There is a better way that using the QueryString jugglery and Session values.
You could just use the previous page property that is set during cross page posting.
Use an asp link button:
<asp:LinkButton runat="server" id="myLink"
NavigateUrl="~/Page2.aspx"
target="_blank" Text="Go to page 2"></asp:LinkButton>
Then on Page2.aspx.cs:
Get the values from the Page.PreviousPage as follows:
TextBox txtUser = (TextBox)Page.PreviousPage.FindControl("txtUser");
TextBox txtSomeValue = (TextBox)Page.PreviousPage.FindControl("txtSomeValue");
Use these as you require in your second page.

Dynamic data for JQuery in ASP.NET pages

Problem
I have some pages that need dynamic data from website to generate output to users.
A simple solution is an aspx(php, ...) page to generate data and create another html page serving as GUI retrieving data from first page and showing it to users. in this method I can call my GUI page for example form1.aspx and my data page form1.json.aspx.
although I personally like this method, it is not suitable when creating components for it.
Another method that currently I'm using is using same GUI page call itself with a querystring to retrieve data. this page should check for that query string and if it exists, only generate data and remove everything else from page. As an example for this method if I call my page form1.aspx, to retrieve data, I need to call it like form1.aspx?JSON
Here is an example of what I'm doing:
protected void Page_Load(object sender, EventArgs e) {
if (Request.QueryString.ToString().IndexOf("JSON") == 0){
this.Controls.Clear();
Response.Clear();
// send pure data to client
} else {
// render page as GUI
}
}
However this method becomes too messy if I add master page and/or inherit my page from some template page. Master pages can only removed in Page_PreInit and that adds another extra method.
Security controls cause another problem, if user leaves page open for long time until session expires any attempt to retrieve data will fail cause security module will redirect the request to login page.
Next problem is I cannot consolidate my component in package because it needs modification in page (removing master page, clearing page components ...).
What I'm looking for:
1- I'm looking for a solution that I can call my page and get pure data (JSON or XML format) and doing so run a server side method that generates data, so I don't have to worry about what another designer puts in their master page or template.
2- I think it is possible to use axd extension to do this but I don't have a clue about it and couldn't find a helping document either.
3- Is there any better way of doing this. any suggestion or solution to improve this much appreciated.

Page methods. Check this article: http://weblogs.asp.net/craigshoemaker/archive/2008/09/29/using-jquery-to-call-asp-net-ajax-page-methods.aspx or http://encosia.com/using-jquery-to-directly-call-aspnet-ajax-page-methods/
WCF JSON service: http://www.codeproject.com/Articles/327420/WCF-REST-Service-with-JSON
Other ways of doing is using an HTTP Handler. Implement IHttpHandler interface and register your implementation in your Web.config file. Later call it using jQuery ($.get / $.post):
http://msdn.microsoft.com/en-us/library/46c5ddfy.aspx
EDIT
As OP pointed out, in order to access session state in a page method you should use WebMethodAttribute this way:
[WebMethod(EnableSession = true)]

I think you can use webservice instead of aspx page to return a JSON or XML string and then the caller page (any aspx page) will response after process is success.
So with this webservice, any third party page will have access to your server side method.
To create a webservice pls Check this link: Create and use Asp.net web service basic
Regards

Pass values from the asp.net controls in one webpage to asp.net controls in another webpage

I have a webpage 'WPwp1.aspx' and another webpage 'FLcourt.aspx'
In WPwp1.aspx i have DropDownList2,DropDownList3,TextBox1,TextBox2,TextBox3 and a LinkButton1
On click of a link button i want to
redirect to FLcourt.aspx.
FLcourt.aspx also has the controls
that are there in
WPwp1.aspx(DropDownList2,DropDownList3,TextBox1,TextBox2,TextBox3)
When user input value in the controls present in WPwp1.aspx and clicks on LinkButton1, the user should be able to see all the values that were being given as input in 'WPwp1.aspx' into the asp.net controls in 'FLcourt.aspx'.
How is it possible to pass values being input in some controls in a webpage to similar controls in another webpage?

Yes, you have several options:
Use Session variables. This is the less scalable way. Just before Response.Redirect, store
your values in Session and get them in the Page_Load of the target page.
Using QueryString. Pass the values in a query string:
Response.Redirect(
string.Format("FLcourt.aspx?value1={0}&value2={1}",
HttpUtility.UrlEncode(value1),
HttpUtility.UrlEncode(value2)));
And in the second page:
var value1 = Request.QueryString["value1"];
UPDATE
Using cookies (the client's browser must have them enabled). Set cookies before Redirect:
Response.Cookies["MyValues"]["Value1"] = value1;
In the target page:
if(Request.Cookies["MyValues"] != null)
{
var value1 = Request.Cookies["MyValues"]["Value1"];
//...
}
(but you have to check that Request.Cookies["MyValues"] is not null before)

You can try this out.
In your source page ("WPwp1.aspx") create properties for each control i.e. DropDownList2,DropDownList3,TextBox1,TextBox2,TextBox3.
Give "PostBackUrl" property of the linkbutton to the page you want to redirect, in your case it will be "FLcourt.aspx".
In the destination page ("FLcourt.aspx") access the previous page with the help of "PreviousPage" class. This class will give you the properties which you have written in point1.
Hope this helps!
Regards,
Samar

See: http://msdn.microsoft.com/en-us/library/6c3yckfw.aspx
To summarize and answer your question directly, you can:
Use a query string.
Get HTTP POST information from the source page.
And since both pages appear to be in the same Web Application, you can also:
Use session state.
Create public properties in the source page and access the property values in the target page.
Get control information in the target page from controls in the source page using the PreviousPage object. This option has a particular performance disadvantage as a call to PreviousPage results in the instantiation of the object and the processing of its life-cycle up to, but not including PreRender.
Sometimes, though, it is simpler to avoid cross-page postbacks and simulate the multiple pages/stages with Panel or MultiView controls.

Use sessions
Use cookies
Use Applications (global)
Post Back URL
Query String
Server.Transfer
Static Variables (global)

http://www.herongyang.com/VBScript/IIS-ASP-Object-Example-Pass-Value-between-Pages.html
its shown how you do it between two pages.

Can I know what page is in my master page's ContentPlaceHolder?

All the Google finds I ran into tell me how to use FindControl to access a control on the master from the content page itself.
However, what I'm trying to do is the opposite.
From the master page, I want to reference whichever child page is in the ContentPlaceHolder.
Why you ask.
I want the master page to know which tab should be active depending on the content Page currently in the placeholder.
This lets me avoid having each page to reference the master page and allow them to change the active tab; that should be the master page's job (if there's a way it can know whom it's enclosing).
Thanks. No rants please.

If you are looking to get the instance of the executing page class, you can retrieve it from the current HTTP context:
var page = HttpContext.Current.CurrentHandler as Page;
From there, you can navigate the page's control tree, call FindControl(), and so on. Be cautious about page lifecycle, though, as master page events tend to fire before their page event counterparts.