Is it possible, with the ASP.NET Ajax library (Sys....) to add controls to the page. For example in JQuery I would perform
$("#mydiv").append($("#anotherdiv input"));
Or something similar. I want to do this without wrapping everything in an UpdatePanel if possible, preferably through clientside scripting. But I have a feeling this will confuse the ViewState.
N.B. This isn't a dupe of this post, which is about something different.
I'm closing this as it is possible, however it's fiddly. Chapter 10 of ASP.NET AJAX in Action covers it a little. Without partial postback though it's impossible
Your correct--it would confuse the viewstate as all the controls need to be on the page during or before the OnInit() method, as far as I can remember.
Yet, you may still be able to use some jQuery/Ajax to pull back the rendered control. Say, for instance, you had a "helper" page, "MyControlsOutput.aspx", and on that page, you had your control embedded into it, ie "". Then, you could, in theory, use jQuery to query the MyControlsOutput.aspx page, and return the responsetext to your page. Again, it would not be in your ASP.Net page's control collection, nor would it have any clue about your viewstate. So, this is probably not what you're looking for, but, it was just a thought.
...While writing the above, I did a quick Google search for "asp.net ajax load control". See if this may help (you may have already seen this, sorry if that's the case):
http://weblogs.asp.net/sanjeevagarwal/archive/2008/07/22/Dynamically-create-ASP.NET-user-control-using-ASP.NET-Ajax-and-Web-Service.aspx
It's a similar concept, but it looks like they are using ASP.Net's ajax calls, and loading it into the page's control collection, and letting it use the page's viewstate as well. Couldn't hurt, eh? :)
Hope that helps a little bit. Good luck.
Related
I'm newbie in ASP.NET and i think that my question is quite simple, but I'm not getting success in my searches through google or even stackoverflow.
I have a asp.net method (vb.net) that loads a entire html page inside a div.
Doing searches, i discovered that it can be like this:
On .aspx page:
<div id="content"></div>
On .vb codebehind:
Private sub LoadContent()
content.InnerHtml = MyDLL.LoadFromDatabase.Value.ToString()
End Sub
So, nothing special until here.
But, if consider that the html code loaded from database has form elements like <input id="name" type="text">, my problem starts...
On page postback these don't keep the values as <asp:TextBox> created natively on code, does.
And the other thing that I want is a way to retrieve the value from them to work on codebehind, like: myvar = content.Controls("name").Value
At least, is there a way to solve my problem?
Sorry for my bad english, and thanks so much.
CRice is right. If you want the viewstate to persist through postback you need to create the controls server-side.
Careful though: I've had bad experience with dynamically created controls on Asp.Net, specifically when trying to bind events to them. Not only would you have to use delegates and events (a hard topic for a newbie), also when I tried it a few years ago I just couldn't get it to work, no matter what.
If you're going for dynamic created controls, make sure it's worth the effort, because it WILL be an effort, now and in the future when you would like to maintain and add expand. A rule of thumb is that dynamic mechanisms are always harder to maintain than static ones, but they provide more flexibility.
Having that said, if you're still going for dynamic html loading, be aware that better solutions exist, though they require different architectures: client side frameworks (best is angluar.js) provide dynamic loading of "modules" (and much more), which is what you want. On the server side, asp.net MVC with its Razor view engine, partial views etc., is better suited for dynamic html generation.
Back to your original question,are you sure you need a full postback? What about a nice neat Ajax call to a web service? Can get the job done in many cases without reloading the whole page. I guess using jquery's $.ajax syntax and creating a simple .asmx web service will be easiest for you.
Last but not least, why use vb.net instead of c#? It sucks man. Give it up while you still can.
I'm using a file manager-type WebControl that does lots of postbacks. It's placed inside a Page that is relatively complex. I would like to prevent the WebControl from causing the whole Page to go through the lifecycle. An UpdatePanel helps a little, but not enough.
Is there any way to isolate the WebControl from the rest of the Page? The only way I can think of is sticking the WebControl in a separate Page and creating an iframe in the original Page. Unfortunately that also means my WebControl properties/settings are no longer in the original Page. If I want two instances of the WebControl with different settings, then I have to create a Page for each setting and reference the correct one in my iframes. Not quite as "drag & drop" as I would like. Any other suggestions?
Hard to tell, you can't prevent a control from going through lifecycle; is there anyway to identify though, that during a certain page postback, you prevent the code from running in each event handler by doing something like:
if (_shouldNotRun == true)
return;
//Event handler code
Essentially, figuring out some way to indicate whether the control should run may be an option. IFrame would work, but yes you have to deal with the issues you mentioned. Can you give more detals to the problem?
HTH.
Not 100% sure what events possible to override that are called on PostBack. A good source for the Life Cycle of a page (http://msdn.microsoft.com/en-us/library/ms178472.aspx)
But it sounds as it would be better to remake your control to create Ajax webservice requests for the functions that are possible to prevent most of the postback's?
Cheers,
Stefan
For example,
If I have a textbox with runat=server on a page, The value will be posted back to the server so I can access the properties in the code-behind.
However, under the following situations, does it still hold true?
A textbox with runat=server but does not appear in the function that is post back to. For example, a button is also on the page, when clicked a post back occurs and within the method that is raised, this textbox was not used.
Within a MasterPage, will a textbox residing on the Masterpage itself be posted back?
Because just thinking, isn't this mechanism bloated in nature?
If all input controls and its value are posted back on every single button click (even when the input control is not needed), doesn't this deteriorate performance?
Having just one Form Tag on the page really restricts us to using this mechanism?
Truly Understanding ViewState is a must read article on the subject of ASP.NET ViewState
There are several options to cut down on the bloat (and yes, there's a lot of it when dealing with lots of controls):
Use AJAX to post only the items required - although be careful to allow clients that don't have JavaScript enabled to still use the page/ site.
The MVC framework allows multiple form tags to be used so you can group sections if needs be.
Set the EnableViewState to false on pages/ controls.
Break up your pages into smaller ones.
Additionally, check out this brilliant graphical representation of the Page Life Cycle in ASP.NET.
Every input on the page is posted back fully unless you use ajax, because of the single form tag. Welcome to asp.net...
As long as the method that you're hitting on the server-side is a non-static member of the page's class, it'll have access to the textbox and all other controls on the page.
And yes, all controls rendered to the browser (whether in the MasterPage, user control, etc.) will be available on post-back.
You may want to look into Understanding ASP.NET View State.
There surely are performance hits with this architecture, but (depending on complexity of the page) it's usually not an issue from the server load perspective, because hardware upgrades are typically cheaper than additional programming hours spend on optimizing application performance.
With that said, (and as others have pointed out) look into using AJAX if you want to avoid whole page-level postbacks to the server.
Yes, it's all posted back, and yes it can cause bloat. I'm sure if you search for ViewState you will find plenty of people ranting about it and how to minimise it :)
Yes your text box will be available in both cases, yes it is bloated. This is where AJAX comes into play. Using AJAX you can send just the data you need.
If you want to send a minimal ammount of data, you could use a Page Method (static method on page decorated so the script manager builds javascript to call it or you could call it using jquery or other methods), or a script enabled web service works nice as well.
You also have viewstate which can get very large. ASP.Net MVC is a new paradigm instead of using WebForms which doesn't have view state, or post backs. It embraces HTTP instead of hidding it giving developers more control.
The textbox data would be posted back as noted. In addition to using Ajax, disabling view state greatly imporoves your page's performance though even then data in properties critical to the functioning of controls (Control state) would still be posted back.
If you didn't have postback for every control on the form, you wouldn't be able to access it in code-behind. I.e. if in your button press you wanted to modify the property of the text control you couldn't do that because ASP.Net would know nothing about the text control.
Since the communication between the server and the client is stateless and every time a page is server the server forgets all about it Postbacks are important if you want to work with the same page again. No matter what programming language you use, this or similar mechanism exists for processing server side code.
If you wish to minimize postback (viewstate size), do this.
Set enableviewstate=false on all controls that you don't want posted back.
Use AJAX and web services wherever possible (and don't use UpdatePanel).
Use HTML control as much as possible instead of ASP.Net controls.
Hmm.. There are some excellent suggestion in other answers and good links too.
You've pretty much hit the nail on the head with vanilla ASP.NET - it's not very good! In both the instances you describe the answer is yes - the textbox will be sent with the form.
The whole postback/ViewState problem is a bit of a pain, one of the first things any competent ASP.NET developer learns to do is avoid them!
I have a page with a number of ListViews that I want users to be able to sort and page through. Rather than postback and rebind the entire page each time, I would like to do it via jQuery/AJAX selectively for the control in question. I am comfortable making the client-side call to a WebMethod in my page - my question is how do I get the returned data back into the ListView via jQuery?
(Note: I don't want to use an UpdatePanel!)
I'm not sure if it'll actually be achievable to update a ListView without a postback, just because of the underlying data model of the ListView control.
You're best option to having a complete AJAX solution would be to use a JavaScript templating engine. I've done a demo on my blog using jTemplates and the MS AJAX Library v4 preview - http://www.aaron-powell.com/blog.aspx?id=1209
But despite common belief you can use an UpdatePanel and have it efficient, I also looked at that here: http://www.aaron-powell.com/blog.aspx?id=1195. The biggest thing to keep in mind when using UpdatePanels is ViewState. If you don't need ViewState saved on a control make sure it's turned off. You can really reduce your post-load by doing that. Also removing whitespace will help.
OK, I am not sure if the title it completely accurate, open to suggestions!
I am in the process of creating an ASP.NET custom control, this is something that is still relatively new to me, so please bear with me.
I am thinking about the event model. Since we are not using Web Controls there are no events being fired from buttons, rather I am manually calling __doPostBack with the appropriate arguments. However this can obviously mean that there are a lot of postbacks occuring when say, selecting options (which render differently when selected).
In time, I will need to make this more Ajax-y and responsive, so I will need to change the event binding to call local Javascript.
So, I was thinking I should be able to toggle the "mode" of the control, it can either use postback and handlle itself, or you can specify the Javascript function names to call instead of the doPostBack.
What are your thoughts on this?
Am I approaching the raising of the events from the control in the wrong way? (totally open to suggestions here!)
How would you approach a similar problem?
Edit - To Clarify
I am creating a custom rendered control (i.e. inherits from WebControl).
We are not using existnig Web Controls since we want complete control over the rendered output.
AFAIK the only way to get a server side event to occur from a custom rendered control is to call doPostBack from the rendered elements (please correct if wrong!).
ASP.NET MVC is not an option.
Very odd. You're using ASP.NET server controls and custom controls, but you're not using web controls? And you're calling __doPostBack manually?
Do you like to do things the hard way?
If I was still using the server control model rather than MVC, I would slap ASP.NET Ajax controls on that sucker and call it a day. What you're doing is like putting a blower on a model T. It may be fun and interesting, but after you're done with all the hard work, what do you really have?
I have been doing some more digging on this, and came across how to inject Javascript in to the client when required. This will obviously play a huge part in making the controls more responsive and less round-trips to the server.
For example: RegisterClientScriptBlock.
Look forward to playing with this more, feel free to get invovled people!