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How to share data between two web pages?

Im trying working on a web app project and trying to figure out how to display my answer on the second web page.
I have put a a text box on my first webpage and have corrected the coding of my application as I have received the correct answers in the textbox after I have debugged it.
Ideally I want to remove this textbox and want my answers which I managed to display on my textbox displayed on a label in the next webpage. Here is the calculation part of my code;
var cost = ((int)duration.TotalMinutes) * 0.35m;
txtCost.Text = cost.ToString("c");
I'd like to make my answer appear in my second webpage and not have it displayed in the first. I have tried using Session["Cost"] = cost; on the button click event handler of the first webpage double cost = (double)(Session["Cost"]);
lblDisplay.Text = cost.ToString("c");
and this on the second webpage but every time I Debug it and run I always get $0.00 displayed on my label. Can someone help me fix this?

Sharing value between two views in MVC application, try following
// To save into the Cache
System.Web.HttpContext.Current.Cache["CostKey"] = cost;
// To retrieve Cache Value
var cachedValue = System.Web.HttpContext.Current.Cache["CostKey"] as double;
For Session State, have a look at this link

In ASP.NET WebForms application, you can pass data around in various ways:
Cache
See the Learning Curve answer for examples.
However, the object put in the cache is not guaranteed to be found again if the server experiences memory shortage or alike. The ASP.NET manages the cache and evicts objects on its own to maintain memory availability. This is in contrast with ApplicationState and SessionState where the objects are kept until they are removed manually, or the Application ends or Session expires.
Session and Application states
You can put any object in the SessionState object and retrieve it elsewhere in your code. However, you need to cast it appropriately as the SessionState accepts object-s. E.g. if you store a number, when you retrieving it, you must do the casting yourself, just as you already did it.
The reason it doesn't work, is perhaps you're trying to retrieve it from within another user's SessionState. Yes, the SessionState is a per-user structure. If you need to add the value as from one device and use it on another, use ApplicationState:
Application["cost"] = cost;
Redirecting Response
Using this technique, you could force the browser to request another page from the server and specify the full query string, including the variables you need. E.g. :
var destination = Server.UrlEncode("/someOtherPage.aspx?cost=34.65");
Response.Redirect(destination);
As an alternative, you can use Server.Transfer("someOtherPage.aspx") to save the roundtrip. However, in that case, the browser doesn't change the address in the address bar so the user is misled that she browses one page, but in fact, it is the someOtherPage.aspx.

I would like to clear my querystring after using it on page load c#

Before I ask this question, I'm not even sure what I'm using is a query string (I'm so clueless on this, what I have is the result of some other confusing StackOverFlow research). It is a parameter I'm passing from my SSRS report viewer to my app via a hyperlink expression. It works and everything is grand except for I'd like to clear it from the url right afterwards.
http://10.155.54.101/Update?CurrencyId=67
And I am getting the parameter with this logic on page load.
if (Request.Params["CurrencyId"] != null)
int CurrencyId = int.parse(Request.Params["CurrencyId"]);
I am successfully capturing that information and populating asp.net controls with it but I want to clear it from the address bar now as it lingers after submitting the update (postback?).
Through another Stack Overflow Answer: Clear QueryString on PostBack , I've attempted to clear the querystring through the following code.
Request.Params.Clear();
But I get a collection is read-only error, which is addressed in the stack overflow question above. So I try to use System.Reflection to change the read only property of the collection with the following code.
PropertyInfo Isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
Isreadonly.SetValue(Request.Params, false, null);
Request.Params.Clear();
I don't get the error but nothing is removed, so I might not be referencing the querystring properly because of however the heck Request.Params works.
Can someone nudge me in the right direction with this? I'm so sorry I'm clueless as heck on this.

You can't just change the URL in the address bar of a browser. You could redirect the browser to the URL without the query string, but seeing how you are using the value to populate controls on the page being render that would mean you would need to still need to have that value.
When you say "it lingers after submitting the update", do you mean the user chooses the currency and is redirected to the the page with this query string? If so could you change this action to a POST instead of a GET? Then you could put the currencyId in the body of the POST. If you can't switch it to a POST, then there are a few ideas I listed below.
If you are using session, you could store the currencyId in the user's session. But that would only make sense if you needed to use this value on other requests; as using session is a big decision and if you can keep your website stateless you should.
With that being said, there are two viable options to keep your site stateless. If you need this value on future requests, you can store it in a cookie. If you only need it on this request, you could have the page do post to the URL without the query string but with the value in the POST body.

Passing parameters to Controller ..but NOT on the URL

Is there a way to pass a parameter to a controller without putting it on the URL?
For example,
http://www.winepassionate.com/p/19/wine-chianti-docg-la-moto
has the value 19 on the URL. If you actually change that value to another, the page displays a different record even it the page name remains the same.
So I would like to NOT pass the ID on the URL but still be able to pass that to the Controller.
What's the recommended way to do so?

You can do a post and send it as a form parameter. I do not recommend this. Posts should be for requests that modify data. In this case you're most likely looking just to get that data. The fact that the id is in the URL is a good thing (see the Stack Overflow URLs for reference). If you really don't want the user to be able to modify it (I hope it's not because you think this makes it more secure, because it doesn't), you could do some simple encryption on it to make it more difficult to guess/produce a valid ID.
Using TempData, as some other suggest, is not a robust solution. It won't work for links on a page, just a GET after POST, and then only once since TempData is deleted after the next request.

Well, you have a couple of options:
Is this a form post? If so, then you can simply add a specific key value pair to your form when you submit it and then data will be passed along.
Is the URL unique to that resource? i.e. Does "Wine-chianti-docg-la-moto" exist as a unique representation of the number 19 in a database somewhere? If so, then you can simply do a lookup of that route component in your database to retrieve the value you need (or push that logic all the way down to the database).
Is that a value that is not expected to change a bunch? You can set that value in Session or in a cookie that would be persisted across pages and then pull it from the respective collection.
Are you redirecting to this page from another request on your server? If so, then you can use TempData to store this temporary value. However, I would recommend against this approach, as it is very transient and not good practice imo.
Lastly, you can obscure the value on the URL if you dont want it to be easily user editable. Encrypt it with some algorithm, and then decrypt it on the destination page. The user will be unlikely to be able to alter the ID by typing in a different value in the URL.

If the page is a GET, and you are following the PRG like you should be (Post-Redirect-Get) then you can use TempData["dataName"] = value; in your [HttpPost] controller and then consume it in your [HttpGet] method. It really depends on how the page is being called.
However, there is nothing wrong in letting the user change that number if it is not security related, and is common practice to show non-vital information in the url like that.

You should use TempData in this case. A good read on this can be found on this blog.
TempData allows you to store a value temporarily between requests and is, by default, erased after being accessed.
// TempData samplepublic ActionResult Featured(){ var featuredProduct = new Product { Name = "Assorted Cupcakes", Description = "Delectable vanilla and chocolate cupcakes", CreationDate = DateTime.Today, ExpirationDate = DateTime.Today.AddDays(7), ImageName = "cupcakes.jpg", Price = 5.99M, QtyOnHand = 12 };

Can I pass a value to a page without using query strings or sessions?

I have created a web application in which there are two menus which load the same page. I need to check a condition in the page so that I can load different data based on the variable passed to this page. However, I don’t want to use a query string, since that would require using a different URL, which would interfere with SEO.
Is there a way to do this without using query strings or session data? I need to pass different values on clicking different links in the master page.

Using the reference in the PreviousPage property, you can search for controls on the source page and extract their value. You typically do this with the FindControl method.
use PreviousPage.FindControl("yourcontrolname")
these link may help you
How to: Pass Values Between ASP.NET Web Pages
PreviousPage Property

You can use javascript to post data to you page or you can use hidden fields or cookies

Along with the two other answers if the URL is of concern with query string parameters (and you dont want sessions - eg due to in-proc storage), then one alternative to increase your rank with web-crawlers is ASP.NET Routing.

you can pass values in many ways. using sessions, cookies, query string, hidden inputs.
i personally feel storing query string for menu navigation its not problem, until unless he comes to know exact querystring parameters.
you can try this other methods,
Passing Values between webforms

Try window.location.hash: https://developer.mozilla.org/en/DOM/window.location
You could store data after the # in a URL. This is what Twitter does.

If your problem with query string is just url changing, you can use post method to send data with using a hidden input. like this:
<form action="products.aspx" method="post">
...
<input type="hidden" id="field1" value="value1"/>
</form>
Or use ajax. You can send http request by means of javascript with ajax. In this case there are no url changing or something. This is an example:
<script type="text/javascript">
function loadXMLDoc()
{
var xmlhttp;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("mainDiv").innerHTML=xmlhttp.responseText; //changing the menu
}
}
params="field1="+document.getElementById("field1").value;
xmlhttp.open("POST","products.aspx",true);
xmlhttp.send(params);
}
</script>

I would suggest looking into canonical links.
Using this, you can have two different URL forms, for example bob.aspx and bob.aspx?input=whatever and search engines will only include one of them (e.g. the first) in its index.

Routing - Explanation for 404 page

I use asp.net 4, c# and Routing for my web site.
My Route result like
A) http://mysite.com/article/58/mytitle (result my article all is fine)
58 and mytitle represent in Id and Title Column in DataBase for my Articles table.
I notice that... if I request:
http://mysite.com/article/2000000000/mytitle (a not existing ID)
I receive an Error page.
If instead I try:
B) http://mysite.com/article/58/mytitttttttle (title misspelled)
I still get my page http://mysite.com/article/58/mytitle
I would need to have my website redirect to a 404 page if both the ID or the TITLE do not not represent any record in my DataSource.
PS: I notice that SO website has a similar behavior, apart that they are able to redirect to a 404 page if the ID for a questions does not match.
My questions:
is this a normal behavior?
how to redirect to 404 pages instead?
if is not possible to use 404 pages would make use canonical urls?
I asked because I'm concerning on this scenario, lets imagine a website link wrongly to my site like
http://mysite.com/article/58/mytitttttttle (title misspelled)
or
http://mysite.com/article/58/mytitttttttle2222 (title misspelled)
both will be index my Search Engine and resulting in duplicate content (and it is not good).
Please provide me a sample of code if possible. I appreciate your comment on this, thanks!

The reason this happens is because it uses the numerical id as the search key (in this case it looks for post 58 no matter what).
What you could do is either
get rid of numerical id, and stick with just text OR
retrieve the post, and verify the "postslug" is correct based on what you pulled out from database.
By using just text, you get a cleaner url. However you have to rely on your database indexing your strings in order to have high performance lookup on your postslug. And you have to worry about duplicate slugs.
By using the hybrid, you have less clean url (extra info), but you don't need to worry too much about integer lookup performance.
Which ever choice you pick, you verify this information in your controller, then either return View, or return HttpNotFound()

Hi I did this recently and used this blog which helped alot
http://weblogs.asp.net/paxer/archive/2010/05/31/asp-net-http-404-and-seo.aspx
http://searchengineland.com/url-rewriting-custom-error-pages-in-aspnet-20-12234

Rather than passing the ID and Title, I would recommend saving the Title as a unique value in the database so you can just have:
http://mysite.com/article/title
What happens if there are two titles? Well, then you can create a loop until you find a unique one incrementing an integer at the end like:
http://mysite.com/article/title-2
This gets around the issue of their being an ~infinite number of possible URLs which all point to the same page (which Google will hate you for)
Alternatively, if you wish to keep your URL with both the ID and Title in place, then on your web form run an if statement which returns how many records in the database match the variables.
Something like:
cmd.CommandText = "SELECT COUNT(*) FROM Table WHERE ID=#ID AND Title=#Title"
if ((int)cmd.executescalar == 0){
Response.Redirect("404.aspx");
}