I have a web page and a modal dialog page. On clicking the save button in the show modal dialog. closes the window and returns a value. Now when the
control reaches the JavaScript function of the parent window . I wnt to perform some database operation on the basis of this returned ID.
I am using the following approach to utilize this returned value.
Keeping it in the hidden field and populating the returned value in hidden control.
keeping a hidden button in the parent window, performing the click event when control comes back to JavaScript function of the parent page. Thus in the server side button handler get the value from hidden field and perform database operation on the basis of returned value.
Is this approach fine. Or I can get rid of hidden field
That's not terribly bad provided the ID returned is not sensitive information that someone can use to modify a record that doesn't belong to him. One can perfectly manipulate this ID on the client side for any other ID and have your logic update a different record from what you intended.
If all you are doing is calling a server side method passing this ID; why don't you do the whole update from the pop-window itself (at that point you already know the ID)?
If the parent window (page) is meant to be updated; you can just perform a normal refresh of the page (ie. use window.location to redirect the user to the same page so he can see the update or use Response.Redirect to the same page.)
What you're probably looking for is called AJAX. With AJAX you can communicate with your web server from within your JavaScript code directly. No HTML form posts are required then. You might want to look at frameworks like JQuery. These have easy implementations (cross browser wrappers) to send HTTP requests via AJAX.
Note: I just noticed, you are using ASP.NET. Take a look at ASP.Net AJAX Page Methods.
Related
I have a RadWindow, in that rad window there is a button that will popup another radwindow. (Inside the parent window,and it is a different page). I should be able to send my datatable to Parent radwindow after closing the child radwindow. Any suggestions?
This greatly depends on your setup and the data you need to pass. Here is a brief overview:
you have a server object and you cannot pass the data through JavaScript: Devise a way to store the data on the server (e.g., in the Cache or Session) so you can access it later in the parent page.
You can pass the data via JavaScript: In this case you can simply handle the RadWIndow's OnClientClose event to get the data and pass it to its close() method from the content page, as shown here: http://www.telerik.com/help/aspnet-ajax/window-client-side-events-onclientclose.html.
In either case, you should use the OnCLientClose event to either work with your data on the client (see this demo http://demos.telerik.com/aspnet-ajax/window/examples/dialogreturnvalue/defaultcs.aspx), or to initiate a postback on the first dialog that will work with the data on the server.
This demo will show you a slightly different way of going through the server and then performing an AJAX request to update the first page: http://demos.telerik.com/aspnet-ajax/controls/examples/integration/gridandwindow/defaultcs.aspx?product=window.
I am little confused about Update Panel usage and usage of Jquery:Ajax() method.
Do both of them are used for Partial Post backs..
Which is the best approach to fallow?
Please help me on this..
An update panel performs a full re-render of the page, takes the section matching the panel and sends it back to the client. The browser then replaces the contents of the update panel with the new html.
jQuery's AJAX method allows you to make any request to any page and handle the response data any way you choose. This might include reading a JSON response from a web service, getting html or anything else you wish. Effectively AJAX gives you a mechanism to emulate the user browsing to a given url with GET or POST data and manipulate the results in any way you desire.
It's worth noting that the update panel is built on top of AJAX (technically Javascript's XMLHttpRequest) object.
There are also some gotchas with update panel, eg if you have a Captcha that is outside the panel; When the panel is updated, the captcha visible to the user doesn't change. The server generates a new page, including a new captcha. When the user submits the form, their verification code is for an old captcha.
In short, you have more control with AJAX and learning how to use it will be beneficial but depending on your use case, an update panel may do what you need for less effort.
I'm retro-fitting a .aspx page with AJAX functionality (using VB, not C#). The codebehind populates the page with data pulled from a web-service. The page has two panels that are populted (with different data, of course) in this way. On a full page refresh, one or both panels might need to be populated. But populating Panel 2 can take a long time, and I need to be able to update panel 1 without refreshing Panel 2. Hence the need for AJAX (right?)
The solution I've come up with still has the old .aspx page with .aspx.vb codebehind, but introduces a Generic Handler (.ashx) page into the mix. Those first two components do the work on the user's first visit or on a full page refresh, but when AJAX is invoked, the request is handled by the .ashx page.
First question: Is this sound architecture? I haven't found a situation online quite like mine. Originally, I wanted to make the .aspx page into the AJAX handler by having the codebehind implement IHttpRequest, and then providing "ProcessRequest" and "IsReusable" methods, but I found I couldn't separate a regular visit to the page from an AJAX request, so my AJAX handlers took over even on the first visit to the page. Second question: Am I right to think that this approach (making the .aspx page do double-duty as the AJAX handler) will never work? Is it impossible to tell whether we're getting a full-page request or a partial-page (AJAX) request?
If the architecture is good, then I need to dynamically generate a lot of HTML in the .ashx file, right? If that is right, should I send HTML back to the client, or should I encode it in some way? I've heard of JSON encryption, but haven't figured out how to use it yet. So, Third question: Is "context.Response.Write" the only pipeline for sending data back to the client? And, if so, should I send back HTML or some kind of JSON-encoded objects?
Thanks in advance.
It sounds as if the page requires some AJAX functionality added to the UI.
Suggest using an UpdatePanel for each web form element that needs to have AJAXy refresh
functionality. That'll save you from having to refactor a bunch of code, and introduce a whole lot of HTML creation on your .ashx.
It'll be more maintainable over the long run, and require a shorter development cycle.
As pointed out by others, UpdatePanel would be a easier way - but you need to use multiple update panels with UpdateMode property set as conditional. Then you can trigger the update-panel refresh using any button on the page (see AsyncPostBackTrigger) or even using java-script (see this & this). On the server side, you may decide what has triggered the partial post-back and act accordingly by bypassing certain code if not needed.
You can also go with your approach - trick here is to capture the page output using HttpServerUtility.Execute in your ashx and write it back into the response (see this article where this trick has been used to capture user control output). Only limitation with this approach is that you can only simulate GET requests to your page and so you may have to change your page to accept parameters via query string. Personally, I will suggest that you create a user control that accept parameters via method/properties and will generate necessary output and then use the control on your page and in ashx (by dynmaically loading it in a temperory page - see this article).
EDIT: I am using jquery to illustrate how to do it from grid-row-view.
$(document).ready(function() {
$("tr.ajax-grid-row").click(function() {
$("#hidden-field-id").val($(this).find(".row-id").val()); // fill hidden filed
$("#hidden-button-id").click(); // simulate button click
});
});
You can place above script in the head element in markup - it is assuming that you have decorated each grid-row-view with css class "ajax-grid-row" and each row will have hidden field decorated with css class "row-id" to store row identifier or the value that you want to pass to server for that row. You can also use cell (but then you need to use innerHTML to get the value per row). "hidden-field-id" and "hidden-button-id" are client ids for hidden field and submit button - you should use Control.ClientID to get actual control ids if those are server controls.
JSON is not for that purpose, it is to pass objects serialized with a nice light weight notation, is you need to stream dinamically generated html using ashx, response.Write is what you have. You may want to take a look at MVC
Or you could use jquery if it's just html, the simpliest would be the load function, or you can look into Ajax with jquery. Since the ashx can be served as any resource it can be used in the load function.
I agree with #p.campbell and #R0MANARMY here. UpdatePanel could be the easiest approach here.
But then like me, if you don't want to go the UpdatePanel route, I don't see anything wrong with your approach. However, generating the html dynamically (entirely) at the back end is not a route I'll personally prefer (for the maintainence reasons). I'd rather prefer implementing a solution that will keep the design separate from the data.
I need to develop a page which has 2 dropdownlist.
Options of dropdownlist 2 are based on selection of dropdownlist 1.
I have 2 methods to change the dropdownlist 2. What will you choose?
1:
Postback when users select dropdownlist 1 and change dropdownlist 2.
Pros:
Can use the postback feature, can use the asp.net validator
Cons:
Need to communicate with server (more traffic)
Users will see the page loading in the status bar.
2:
Get all the data (not very much data) in a JSON object when loading the page and change the dropdownlist 2 using javascript.
Pros:
Don't need to communicate with server(less traffic)
Cons:
Can't use the postback feature and validator and more troublesome to write server validation.
Also, I usually write the JSON object to the page as follows:
var locations = <asp:Literal runat="server" id="litLocation" text="[]" />
And then set the "litLocation" in page_load after the data is processed by datacontractjsonserializer.
Do you do it in the same way?
I prefer the second option, no need to reload the whole page just to refresh one dropdown list. I'd also do the client side dev in jQuery, much easier. You can do the client side validation for the change event of the first dropdown in jQuery as well, and keep the form submit validation in ASP.NET.
Have a look at the selectChain plugin for jQuery (demo's etc here).
Why not have your javascript call the server when the select box is clicked on, using a GET method, and fill in the select box, using json as the response, then, when an option is picked then fill in the second select box with another ajax request.
This would be scalable, in that if you want to add more options you just change the server, and everything is centralized.
You will need to validate when the form is submitted anyway, as it is possible to change a value of a form to something illegal using some debugging tools, such as Firebug, so never trust anything from a webpage until you have validated it.
So, no point worrying about the validation until the form is actually submitted.
I have an asp.net server control (with the asp: in its definition). The button has been set to do post back.
On the server side, I have the on click event handler
e.g btnSave_click()
On the client side, I have a javascript function to be invoked on the click event
e.g btnSave.Attributes.Add("onclick","javascript: return CheckIsDirty();")
Am not sure which order these two will be executed. Because I want first on the client side to warn of any data entry fields that are not yet filled-out before actually saving any data.
Any help?
First client side, second server-side.
So you can use it.
I also use it in some cases, like:
close.Attributes["OnClick"] = "return confirm('Are you sure?')";
In this case if the user presses 'No' then the server-side event handler does not even play a role.
The trick here is to set this global variable "Page_IsValid" false if your test fails and this will stop the post back.
Read this page http://msdn.microsoft.com/en-us/library/aa479045.aspx which explains both server side and client Validation. There is sone good code example you can use.
The way you are setting your onClick JavaScript event will actually prevent it from posting back as you are overwritten the ASP.NET event handler. The correct way to accomplish the validation you are intending is to:
btnSave.Attributes.Add("onclick", "CheckIsDirty();" + GetPostBackEventReference(btnSave).ToString());
Notice that you append the result of GetPostBackEventReference, so that in JavaScript you first call your CheckIsDirty() method and then call the ASP.NET postback method. Assuming your method returns true, then the button will post. If it returns false then it will not cause a post back.
Does that sound like what you are trying to accomplish?
I think you need a much better understanding of what it means client side and what it means server side and how they all relate together. I've seen more and more developers make a mess of it.
Of course the client side will execute first in your case. Actually there's no way to execute it after the server code is executed (except if you do something manually). I'll try to give a brief explanation:
Whatever you have in your server, will generate some HTML on the client and the user is always interacting on the client. So you have a html button that the user is clicking. What the browser will do is execute the javascript associated with it or if no javascript is specified and the button is a submit button it will submit the form. if you check the generated html you will see that for the onclick event you will have the script you have added followed by some autogenerated script that actually will submit the form to the server. Your server side code will execute only if the page will be submitted.