I've seen it time and time again the typical answer being something like this:
public string RenderControlToHtml(Control ControlToRender)
{
System.Text.StringBuilder sb = new System.Text.StringBuilder();
System.IO.StringWriter stWriter = new System.IO.StringWriter(sb);
System.Web.UI.HtmlTextWriter htmlWriter = new System.Web.UI.HtmlTextWriter(stWriter);
ControlToRender.RenderControl(htmlWriter);
return sb.ToString();
}
... This is fine if you have simple html tags but when I have a textbox or some other asp control in my control it throws a wobbly about the control not being on a form (which in fact it is because im trying to render a portion of the page to a string that i can then send as an email)
So ...
I'm pretty sure this has been asked and answered before but i'm at a loss for finding a real answer that actually works ...
How do i render the html output of both server and client side controls to a html string in .Net 4.0 because seemingly the above is not good enough?
Note:
I have found examples that talk about doing this at page level ...
public override void VerifyRenderingInServerForm(Control control)
{
//Do nothing (we dont care if theres a form or not)
}
... and disabling event validation but apparently that's not working for me either.
Is there a way to do this without a "hack" thats clean?
Also:
I even tried creating a new page, adding a form to it, added my control to that then calling renderControl on that page to which i got more errors.
EDIT:
I've been digging around and I think the problem might be related to postbacks or something because i found this:
http://forums.asp.net/t/1325559.aspx
Another thing that might be putting a bit of a spanner in the works is my use of the ajax toolkit, I essentially need only the visible portion of the control which seems to give a bit of a headache for updatepanels for some reason.
I'm guessing the above sample works only on basic .net controls that are not ajax toolkit related.
What further complicates the issue is that I would like to get the control in its current state when a button is clicked at the bottom of it ...
Essentially the control represents a form for booking an MOT and I would like to render the form filled in to an email that is then sent to the garage if that makes sense.
I'm thinking i may have to admit defeat here and simply get the markup from the client and manually build an email pulling out the control values as this seems to be a compatability issue between ajax controls and the renderControl method from what i can tell (maybe you cant render a partial postback compatible control in this fashion).
Unless someone smarter than me can prove it can be done ???
Create an ajax control extender and get the html markup on the client side then post that back to the server for processing, it's a bit of hack but it seems that anything involving ajax controls will cause the default recommended mechanism to break.
Related
probably a simple oversight I've missed (though I vaguely recall some obscure blogpost about the inner workings of Response.Write not working as expected in some situations but I don't remember if this is one of them):
The situation is, I have a Link Button on a control running in SP2010, and if I don't use HttpContext.Response.Write(), everything works as expected (ie I can change the .Text value for a Label). However, if I call Context.Response.Write(), while I can debug and step through the code, nothing seems to happen any more (nothing is written back and changes to other controls do not appear). It's being run on an application page in _layouts, appearing in a modal dialog.
(basically, I'm trying to do this - http://acveer.wordpress.com/2011/01/25/using-the-sharepoint-2010-modal-dialog/ but it doesn't work. EDIT: If I change it to a asp:Button, it still doesn't work)
Here's some code if you're interested:
.aspx:
# Page Language="C#" AutoEventWireup="true" ...
<asp:LinkButton CssClass="button remove" runat="server" OnClick="remove_Click" Text="Remove" ID="remove"></asp:LinkButton>
.aspx.cs:
public void remove_Click(object sender, EventArgs e)
{
....
//if successful
HttpContext context = HttpContext.Current;
if (HttpContext.Current.Request.QueryString["IsDlg"] != null)
{
testControl.Text = "test code";
//doesn't work, and prevents line above from working
Context.Response.Write("<script type='text/javascript'>alert('hi!');</script>");
Context.Response.Flush();
Context.Response.End();
// context.Response.Write("<script type='text/javascript'>window.frameElement.commitPopup()</script>");
// context.Response.Flush();
// context.Response.End();
}
}
Anyone come across something similar?
EDIT: some more interesting pieces that may help,
The button itself lies within an UpdatePanel
I do have a AsyncPostbackTrigger assigned
Using Response.Write from Web Forms code behind is problematic at best. As a rule of the thumb: never ever use Response.Write from a Web Forms page or user control.
The reason Response.Write is problematic, is because it is not part of the page's control tree, and rendering infrastructure. This means that when used within events in it will output the text outside of the normal page flow, and usually outside of the proper HTML page structure.
This is also why things go awry when you're using them in combination with UpdatePanels. As UpdatePanels are specifically designed to replace parts from a page, the infrastructure needs to know which parts. A Response.Write happens completely outside of this, and there's no real way of knowing where to render it. At best, the ScriptManager will perform a Response.Clear to wipe out your Response.Writes, at worst you'll break the UpdatePanel protocol body and you'll get a JavaScript error.
To top things off, any literal <script> tag will be ignored when you're performing a partial page update, as the browser's innerHTML feature used to fill in the HTML fragments sent by the server does not execute <script> tags.
Now, with all this theory out of the way -- is there no way to execute a piece of JavaScript code through an UpdatePanel? It turns out there is, and it's a lot cleaner than just executing a Response.Write: ScriptManager.RegisterClientScriptBlock and ScriptManager.RegisterStartupScript. For example:
ScriptManager.RegisterClientScriptBlock(
theButton, // control or UpdatePanel that will be rendered
typeof(YourPage), "UniqueKey", // makes your script uniquely identifiable
"alert('Testing!');", true);
The important part is the first argument: now the ScriptManager will know when to execute your script. If you register it on a control that is not updated on a partial page refresh, your script will not execute. But if the UpdatePanel containing the control is refreshed, your script that is hooked up to it will also execute. And that's usually exactly what you want.
If you always want to execute your script, regardless of which panel updates, you'd call
ScriptManager.RegisterClientScriptBlock(Page, ... );
#Ruben provided a very good answer, but I felt I could add useful content that doesn't fit in a comment.
There are a few occasions in SharePoint where you use a Response.Write - namely when dealing with webparts that are displayed within a SharePoint Modal popup and you want to do something cute with the callback when using window.frameElement.commitPopup().
The fact that you are using Response.Write within an update panel is actually part of your issue. When a postback that was generated with an update panel returns, the response is formatted with UpdatePanelId|Response Content where UpdatePanelId is the div associated with the update panel and Response Content is the new inner HTML of the div. When you use response.write, that format is lost, therefore the ScriptManager has no idea what to do with the response and should ignore it as erroneous. #Ruben provided you a method of registering scripts within an UpdatePanel.
Context.Response... should have a lower case context
ie:
context.Response.Flush()
etc
or am I missing the point?
I wish I could paste in my markup, but it's too complex and contains a lot of references to the client's company name. I am hoping someone with vast experience might be able to point me in the right direction.
We have a master page with a ValidationSummary that is not part of a validation group. On our content page, we have another ValidationSummary that is assigned to a validation group called ValReject. On the content page is also a CustomValidator that uses ClientValidationFunction and a button, both of which are also assigned to ValReject.
When I click the button, the client function executes once, but the error reports to both validation summaries, the one on the content page and the on on the master page. I even added a third validation summary and set its group to something like "asdf", but it gets reported to, as well, meaning all three validation summaries are showing the same error on the page.
I then created a separate ASP.NET test project, pasted all the code in, and ran it and it validates like it should.
I then played around with AutoEventWireup on the content page. When I set it to false, validation works, but the page load event doesn't fire. What's up with that?
I know you probably need code samples, but, like I said, I just can't do that without going through a huge headache (trust me, the master and content page markup is huge.
The question here is: Does anyone have an idea of what could cause a single validator to report to ALL validation summaries on the page even though only one of them shares the same validation group as the validator and button?
edit: When I pasted the markup into my test app, I did have to remove some tags to get it to work since the test app doesn't have references to some assemblies used by the real master page. Some things I removed are:
<%# Register Assembly="RadMenu.Net2" Namespace="Telerik.WebControls" TagPrefix="radM" %>
<radM:RadMenu ID="RadMenu1" runat="server" DataSourceID="smdsMenu" Skin="CssGrey" ClickToOpen="True" EnableViewState="False" CausesValidation="false" />
So the fact that it works on my test app leads me to the conclusion that we're doing something on our production app that I am not doing in my test app. Yes, I know this is vague, but perhaps a light bulb will go off in someone's head.
Man, after hours and hours of spinning my wheels, I finally figured it out. We use this extension method to disable double clicks of buttons:
public static void DisableDoubleClick(this Button Control)
{
System.Text.StringBuilder sb = new System.Text.StringBuilder();
sb.Append("if (typeof(Page_ClientValidate) == 'function') { ");
sb.Append("if (Page_ClientValidate() == false) { return false; }} ");
sb.Append("this.disabled = true;");
sb.Append(Control.Page.ClientScript.GetPostBackEventReference(Control, ""));
sb.Append(";");
Control.Attributes.Add("onclick", sb.ToString());
}
This is what was messing up the validation as it was invoking global validation. I fixed this by making the following change:
sb.Append(string.Format("if (Page_ClientValidate({0}) == false) {{ return false; }}}} ",
Control.ValidationGroup == string.Empty ? string.Empty : string.Format("\"{0}\"", Control.ValidationGroup)));
What clued me in was when I set AutoEventWireup to false to see what would happen. This kept the page load event from firing which is where the above extension method was being called. What a needle in the haystack, this problem.
I don't blame anyone for not answering due to lack of details, but I will keep this up in case anyone else can use it.
edit: Thanks to slfan and gbs. I had just figured out the issue and was coming back here to post my answer when I see that you two were essentially tackling my issue from both sides of the problem. The page load event is where the binding was occurring and the extension method being called was messing up the Page_ClientValidate function. Since you both are technically right and I can't award both of you the answer, I hope no one gets upset if I mark my own as the answer here. You two are definitely good at analyzing such issues with minimal details and no code samples. Props.
The AutoEventWireup causes ASP.NET to call the Page_Load event automatically without having to register to an event. An alternative could be to override the OnLoad method. Your page seems to work properly when Page_Load is not called. What do you do inside this method? Some strange data bindings? What if you uncomment this code, will it work then? Like this you could narrow your problem down to the real problem which you are not showing in your question.
Two things I would look for:
1: Any external validation using Page_ClientValidate being done in javascript
2: Any explicit call to Page.Validate() in code-behind
I am creating a ASP.NET Web Form application where I am trying to use some nice jQuery functionality and flashyness. The current part of the application I have consists of two jQuery UI tabs; a search tab and a results tab. When the user performs a search from the search page, the results tab will be selected and the results will be displayed in this tab. I need to get the results into a gridview. Now this is where the issue starts to come in:
The easiest way to get the search results is to allow the search click to perform the postback where I can then format the datasource with the parameters from the input fields and let the datagrid take care of itself and data bind and show the results. The thing is, this really doesn't look that great (due to the whole post back and such) as well as starts to cause some issues with using javascript/jQuery to take care of tab switching and all that portion because the postback reinitializes everything from the jQuery UI (i.e. the jQuery UI tabs). So in short, the postback allows for easy binding of the input for the search and getting the results, but makes the page and its behavior all wonky.
I was wondering if there is a standard way to do this type of mixing jQuery/javascript/AJAX all together within web formto get the functionality of things like the gridview and such. I am wondering if there are some good tutorials, or even just a direction on solving this issue.
I hope all this made sense, and thank you all for your help.
I don't think this is a standard, but here is the pattern I use:
First of all, I use Page Methods for ASP.Net to get hooked back up to the server. In this case it would be something like this:
PageMethods.Search(searchValue, onSearchComplete);
That calls a static page method in the page, like this:
public static void Search(string searchValue)
...
Inside that procedure, I create an instance of a user control which contains the gridview, and invoke a method on that control, passing the searchValue:
var searchControl = (SearchControl)new SearchControl().LoadControl("/controls/SearchControl.ascx");
searchControl.Search();
var stringBuilder = new StringBuilder();
using (var textWriter = new StringWriter(stringBuilder))
{
var htmlWriter = new HtmlTextWriter(textWriter);
searchControl.RenderControl(htmlWriter);
return stringBuilder.ToString();
}
This is all going to end up as the result argument to the handler you specified in the initial call (onSearchComplete) in this example. You can do whatever you want with the markup, including slapping it into a div, or alerting it for debugging.
I have a very big problem. I am making a CRM (Costumer Relationship Management) System in ASP.NET 3.5
I have based my entire project on DevExpress.com controls and the use of UpdatePanels.
Now one of my pages, which is a central page in the whole system, contains a very big amount of possibilities and therefore a big amount of UserControls.
Now my problem is that it's getting really really slow because of the fact that UpdatePanels are reposting the entire page and not only the update panel. We are talking sometime 3-4 seconds before a popup window appears :(
Is there any way I can refactor this entire system away from UpdatePanels without breaking my neck?
Are there anyway I can optimize my use of UpdatePanels?
The ViewState is also absolutely giant.
Any good ideas are welcome...
There's no way to get around posting the entire page using UpdatePanels. In lieu of redesigning the app here are a couple things I'd try:
Disable viewstate for any controls that don't need it
Set the UpdateMode="Conditional" for your user controls. This won't get around posting the entire page but it will cut down on rendering time a little. Only the content for the specific UpdatePanel will be updated in the browser.
Make sure your user controls have short IDs. The way ASP.NET webforms names controls in the html these IDs get repeated quite a bit if you have a lot of server controls. Same goes for naming master page placeholders. I once cut a large page to half the size by renaming user controls and placeholders.
Since you're a DevExpress user, you might consider taking a little time to learn their CallbackPanel which will allow you to do asynchronous processing without the overhead of the UpdatePanel.
Alternatively (someone please correct me if I'm wrong) but if all of the postbacks are asynchronous (i.e. in an UpdatePanel), wouldn't it be theoretically possible to disable ViewState for the entire page (in the Page directive) without negative consequences? You'd have to test it completely off course, but it's worth a shot.
You'll have to replace some of the postbacks contained in your update panels with real AJAX calls, i.e. send only the data that is required for the action to the server and get back only what's required to update the view, getting rid of the postback and the UpdatePanels.
(You'll notice my use of the terms 'action' and 'view' - yes, I am an MVC fan. The situation you are in is typical of the mess that is easily got into using WebForms and the ASP.NET AJAX controls.)
I must be missing something. Why is your updatepanel is reloading the entire page. The point of an updatepanel is to refresh only what is in that panel, isn't it? Thanks for the explanation. I guess we're talking about reposting the page and not redrawing the panel as I thought.
Try turning off ViewState, especially for grids.
What kind of control is most common on your page? Try replacing those with your own lightweight UserControl or Server Control that does not use ViewState or ControlState
For all Interested I want to add a solution on how to get rid of the Viewstate data on clientside. It does give the server an extra load but if you are in the same situation as me and have a lot of server power and need to take the load of the clientside this is nice.
Let all your pages Derive from BasePage.cs looking like this
public class BasePage : System.Web.UI.Page
{
protected override void SavePageStateToPersistenceMedium(object viewState)
{
string vsKey = String.Format("VIEWSTATE_{0}_{1}_{2}", base.Session.SessionID, Request.RawUrl, DateTime.Now);
Session.Add(vsKey, viewState);
ClientScript.RegisterHiddenField("__VIEWSTATE_KEY", vsKey);
}
protected override object LoadPageStateFromPersistenceMedium()
{
string vsKey = Request.Form["__VIEWSTATE_KEY"];
return Session[vsKey];
}
}
Now you have a key to the viewstate data session instead of the viewstate in your code...
Works like a charm for me on a website with 1000-1200 daily visitors as well.
I need to catch the HTML of a ASP.NET just before it is being sent to the client in order to do last minute string manipulations on it, and then send the modified version to the client.
e.g.
The Page is loaded
Every control has been rendered correctly
The Full html of the page is ready to be transferred back to the client
Is there a way to that in ASP.NET?
You can override the Render method of your page. Then call the base implementation and supply your HtmlTextWriter object. Here is an example
protected override void Render(HtmlTextWriter writer)
{
StringWriter output = new StringWriter();
base.Render(new HtmlTextWriter(output));
//This is the rendered HTML of your page. Feel free to manipulate it.
string outputAsString = output.ToString();
writer.Write(outputAsString);
}
You can use a HTTPModule to change the html. Here is a sample.
Using the answer of Atanas Korchev for some days, I discovered that I get JavaScript errors similar to:
"The message received from the server could not be parsed"
When using this in conjunction with an ASP.NET Ajax UpdatePanel control. The reason is described in this blog post.
Basically the UpdatePanel seems to be critical about the exact length of the rendered string being constant. I.e. if you change the string and keep the length, it succeeds, if you change the text so that the string length changes, the above JavaScript error occurs.
My not-perfect-but-working solution was to assume the UpdatePanel always does a POST and filter that away:
protected override void Render(HtmlTextWriter writer)
{
if (IsPostBack || IsCallback)
{
base.Render(writer);
}
else
{
using (var output = new StringWriter())
{
base.Render(new HtmlTextWriter(output));
var outputAsString = output.ToString();
outputAsString = doSomeManipulation(outputAsString);
writer.Write(outputAsString);
}
}
}
This works in my scenario but has some drawbacks that may not work for your scenario:
Upon postbacks, no strings are changed.
The string that the user sees therefore is the unmanipulated one
The UpdatePanel may fire for NON-postbacks, too.
Still, I hope this helps others who discover a similar issue. Also, see this article discussing UpdatePanel and Page.Render in more details.
Take a look at the sequence of events in the ASP.NET page's lifecycle. Here's one page that lists the events. It's possible you could find an event to handle that's late enough in the page's lifecycle to make your changes, but still get those changes rendered.
If not, you could always write an HttpModule that processes the HTTP response after the page itself has finished rendering.
Obviously it will be much more efficient if you can coax the desired markup out of ASP.Net in the first place.
With that in mind, have you considered using Control Adapters? They will allow you to over-ride how each of your controls render in the first place, rather than having to modify the string later.
I don't think there is a specific event from the page that you can hook into; here is the ASP.Net lifecycle: http://msdn.microsoft.com/en-us/library/ms178472.aspx
You may want to consider hooking into the prerender event to 'adjust' the values of the controls, or perform some client side edits/callbacks.