I'm dynamically loading user controls adding them to the Controls collection of the web form.
I'd like to hide user controls if they cause a unhandled exception while rendering.
So, I tried hooking to the Error event of each UserControl but it seems that this event never fires for the UserControls as it does for Page class.
Did some googling around and it doesn't seem promising. Any ideas here?
mmilic, following on from your response to my previous idea..
No additional logic required! That's the point, your doing nothing to the classes in question, just wrapping them in some instantiation bubble-wrap! :)
OK, I was going to just bullet point but I wanted to see this work for myself, so I cobbled together some very rough code but the concept is there and it seems to work.
APOLOGIES FOR THE LONG POST
The SafeLoader
This will basically be the "bubble" I mentioned.. It will get the controls HTML, catching any errors that occur during Rendering.
public class SafeLoader
{
public static string LoadControl(Control ctl)
{
// In terms of what we could do here, its down
// to you, I will just return some basic HTML saying
// I screwed up.
try
{
// Get the Controls HTML (which may throw)
// And store it in our own writer away from the
// actual Live page.
StringWriter writer = new StringWriter();
HtmlTextWriter htmlWriter = new HtmlTextWriter(writer);
ctl.RenderControl(htmlWriter);
return writer.GetStringBuilder().ToString();
}
catch (Exception)
{
string ctlType = ctl.GetType().Name;
return "<span style=\"color: red; font-weight:bold; font-size: smaller;\">" +
"Rob + Controls = FAIL (" +
ctlType + " rendering failed) Sad face :(</span>";
}
}
}
And Some Controls..
Ok I just mocked together two controls here, one will throw the other will render junk. Point here, I don't give a crap. These will be replaced with your custom controls..
BadControl
public class BadControl : WebControl
{
protected override void Render(HtmlTextWriter writer)
{
throw new ApplicationException("Rob can't program controls");
}
}
GoodControl
public class GoodControl : WebControl
{
protected override void Render(HtmlTextWriter writer)
{
writer.Write("<b>Holy crap this control works</b>");
}
}
The Page
OK, so lets look at the "test" page.. Here I simply instantiate the controls, grab their html and output it, I will follow with thoughts on designer support etc..
Page Code-Behind
protected void Page_Load(object sender, EventArgs e)
{
// Create some controls (BadControl will throw)
string goodHtml = SafeLoader.LoadControl(new BadControl());
Response.Write(goodHtml);
string badHtml = SafeLoader.LoadControl(new GoodControl());
Response.Write(badHtml);
}
Thoughts
OK, I know what you are thinking, "these controls are instantiated programatically, what about designer support? I spent freaking hours getting these controls nice for the designer, now you're messing with my mojo".
OK, so I havent really tested this yet (probably will do in a min!) but the idea here is to override the CreateChildControls method for the page, and take the instance of each control added on the form and run it through the SafeLoader. If the code passes, you can add it to the Controls collection as normal, if not, then you can create erroneous literals or something, up to you my friend.
Finally..
Again, sorry for the long post, but I wanted to get the code here so we can discuss this :)
I hope this helps demonstrate my idea :)
Update
Tested by chucking a control in on the designer and overriding the CreateChildControls method with this, works fine, may need some clean up to make things better looking, but I'll leave that to you ;)
protected override void CreateChildControls()
{
// Pass each control through the Loader to check
// its not lame
foreach (Control ctl in Controls)
{
string s = SafeLoader.LoadControl(ctl);
// If its bad, smack it downnnn!
if (s == string.Empty)
{
ctl.Visible = false; // Prevent Rendering
string ctlType = ctl.GetType().Name;
Response.Write("<b>Problem Occurred Rendering " +
ctlType + " '" + ctl.ID + "'.</b>");
}
}
}
Enjoy!
This is an interesting problem.. I am still pretty fresh when it comes to custom controls etc, but here are my thoughts (feel free to comment/correct people!).. (I am kinda thinking/writing out loud here!)
If an error occurs during rendering, in some cases, would it not be too late? (since some of the controls HTML may have already been sent to the Writer and output).
Therefore, would it not be best to wrap the user control's Render method, but rather than passing it the reference to the "Live" HtmlTextWriter, you pass your own, trap any Exceptions raised in this little safety "bubble", if all goes well, you then pass your resultant HTML to the actual HtmlTextWriter?
This logic could probably be slung to a generic wrapper class which you would use to dynamically load/render the controls at run time..
If any errors do occur, you have all the information you need at your disposal! (i.e control references etc).
Just my thoughts, flame away! :D ;)
Depending on where your errors are occurring you can do something like...
public abstract class SilentErrorControl : UserControl
{
protected override void Render( HtmlTextWriter writer )
{
//call the base's render method, but with a try catch
try { base.Render( writer ); }
catch ( Exception ex ) { /*do nothing*/ }
}
}
Then inherit SilentErrorControl instead of UserControl.
Global.asax and Application_Error?
http://www.15seconds.com/issue/030102.htm
Or the Page_Error Event on an individual Page only:
http://support.microsoft.com/kb/306355
void Page_Load(object sender, System.EventArgs e)
{
throw(new ArgumentNullException());
}
public void Page_Error(object sender,EventArgs e)
{
Exception objErr = Server.GetLastError().GetBaseException();
string err = "<b>Error Caught in Page_Error event</b><hr><br>" +
"<br><b>Error in: </b>" + Request.Url.ToString() +
"<br><b>Error Message: </b>" + objErr.Message.ToString()+
"<br><b>Stack Trace:</b><br>" +
objErr.StackTrace.ToString();
Response.Write(err.ToString());
Server.ClearError();
}
Also, Karl Seguin (Hi Karl!) had a Post on using HttpHandler instead:
http://codebetter.com/blogs/karlseguin/archive/2006/06/12/146356.aspx
(Not sure what the permission to reproduce it, but if you want to write up an answer, you got my Upvote ☺)
How about adding a new sub-class of UserControl that error-handles its render and load methods (so that they hide as you wish) and then inheriting from that for your user controls?
I am not sure I understand your response.. How are you loading your controls and adding them to your controls collection?
That was the whole point of the bit added in the "Update" section.. You have the flexibility to use the SafeLoader wherever you please.
I am not sure why you feel you don't have access/control over the Html? The goal of the SafeLoader is that you dont care what the html is, you simply try and "output" the control (within the "bubble") and determine if it loads OK in its current state.
If it does (i.e. the html is returned) then you can do what you like with it, output the html, add the control to the controls collection, whatever!
If not, then again, you can do what you like, render an error message, throw a custom exception.. The choice is yours!
I hope this helps clarify things for you, if not, then please shout :)
I used #Keith's approach, but the problem is that the control is rendered up until the Exception is thrown, potentially resulting in open HTML tags. I'm also rendering the exception information in the Control if in Debug mode.
protected override void Render(System.Web.UI.HtmlTextWriter writer)
{
try
{
// Render the module to a local a temporary writer so that if an Exception occurs
// the control is not halfway rendered - "it is all or nothing" proposition
System.IO.StringWriter sw = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htw = new System.Web.UI.HtmlTextWriter(sw);
base.Render(htw);
// We made it! Copy the Control Render over
writer.Write(sw.GetStringBuilder().ToString());
}
catch (System.Exception ex)
{
string message = string.Format("Error Rendering Control {0}\n", ID);
Log.Error(message, ex);
if (Page.IsDebug)
writer.Write(string.Format("{0}<br>Exception:<br><pre>{1}\n{2}</pre>", message, ex.Message, ex.StackTrace));
}
}
Related
I have a webusercontrol with a public int property SelectedCatID. I use this control on other pages and in other controls as follows:
<NewStore:LeftMenuLinks runat="server" SelectedCatID="<%#CatIDToSelect%>" />
How do I output cache this control based on SelectedCatID? Everything I've tried fails.
The closest I've gotten is getting it to cache, but it doesn't vary on SelectedCatID leaving the same menu item selected until the cache expires. Without caching, the control works as expected.
I figured out why the VaryByControls approach you used initially does not work. Sadly you edited it out of your question, so my research for this will just have to go into a blog post. Update: the blog post in question: http://tabeokatech.blogspot.be/2014/09/outputcache-on-user-controls.html .
The long and short of it though is that VaryByControls is kinda shorthand for VaryByParams, and does nothing for properties: it only looks at POST values. The fact that it ever worked for properties with a static value appears to be a bug - any string whatsoever in the VaryByControls would have made that part work. The accepted answer to this question is wrong: Vary by control properties using PartialCaching in ASP.NET .
There is no built-in way to vary by control property values.
That wouldn't make sense anyway, because user controls need to be created to have property values, and you want to avoid creating them, instead caching their rendered markup - cached user controls fields are null in code-behind if cached markup is served for them.
This works by injecting a PartialCachingControl into the page instead of the actual user control. This PartialCachingControl checks the cache, and only creates the control if no cached version exists.
As for making it work, I see two options:
If you only have 1 usercontrol per page, you could use the VaryByCustom approach. To make things easy you could write an interface that returns your property value for that page, and implement it on every page that hosts the user control, e.g.:
interface INumberProvider
{
int GetNumber();
}
// and the page:
public partial class _Default : Page, INumberProvider
{
public int GetNumber()
{
return this.SomeNumberPropertyOrWhatever;
}
...
In your Global.asax you cast the current handler to INumberProvider and get the number:
public override string GetVaryByCustomString(HttpContext context, string custom)
{
if (custom == "INumberProvider")
{
var page = context.CurrentHandler as INumberProvider;
if (page != null)
{
return page.GetNumber().ToString();
}
}
return base.GetVaryByCustomString(context, custom);
}
And in your control you obviously add:
OutputCache Duration="180" VaryByCustom="INumberProvider" VaryByParam="None" Shared="true"
That's if you only have one user control per page, and should be pretty straightforward. If you need more than one user control per page you're out of luck:
Build your own wrapper around your user control by writing a custom WebControl. Add the properties you need, capture the output of the rendered user control, and insert it into HttpContext.Current.Cache with a key that includes the SelectedCatID. Basically write your own custom PartialCachingControl.
There's also option 3:
Decide caching is not that important after all
<%# OutputCache Duration="60" VaryByParam="SelectedCatID" %>
Now store youre <%#CatIDToSelect%> as an a parameter ex ?SelectedCatID=12
Now you're Page or UserControl depending on what you want to cache will output the cache depending on what the Request.Param["SelectedCatID"] is equal to.
You can also do something like this (although not the easiest way)
This goes on the page/usercontrol you want cached:
<%# OutputCache duration="120" varybyparam="None" varybycustom="SelectedCatID" %>
This goes into the Gloabal.asax file:
public override string GetVaryByCustomString(HttpContext context, string custom)
{
if(custom == "SelectedCatID")
{
return CatIDToSelect;
}
return String.Empty;
}
I'm late to the party here what with an accepted answer and a 500 point bounty awarded. Still wanted to give my few cents on how this could be achieved.
It can be made to work in the control itself. You can have the control store it's own output in the cache and use the cached version in the Render method if found. I have made a really simple UserControl to test with. The markup looks like this:
<%# Control Language="C#" AutoEventWireup="true" CodeBehind="TestUC.ascx.cs"
Inherits="Webforms_Test.UserControls.TestUC" %>
<div>
<asp:Label ID="curTime" runat="server"></asp:Label>
</div>
It just contains a label that is set to DateTime.Now when it is initialized. The code behind looks like this:
public partial class TestUC : System.Web.UI.UserControl
{
private string cachedOutput = null;
public bool RenderFromCache = true; // set to false in containing page if this control needs to be re-rendered
protected void Page_Load(object sender, EventArgs e)
{
cachedOutput = HttpContext.Current.Cache["key"] as string;
if (cachedOutput == null)
{
// not found in cache, do the heavy lifting here to setup the control
curTime.Text = "UC:" + DateTime.Now.ToString("yy-MM-dd hh:mm:ss");
}
}
protected void Page_PreRender(object sender, EventArgs e)
{
if (cachedOutput == null || !RenderFromCache)
{
RenderFromCache = false;
StringBuilder b = new StringBuilder();
HtmlTextWriter h = new HtmlTextWriter(new StringWriter(b));
this.RenderControl(h);
cachedOutput = b.ToString();
HttpContext.Current.Cache.Insert("key", cachedOutput, null, DateTime.UtcNow.AddSeconds(10), TimeSpan.Zero);
RenderFromCache = true;
}
}
protected override void Render(HtmlTextWriter writer)
{
if (!RenderFromCache)
base.Render(writer);
else
writer.Write(cachedOutput);
}
}
In this sample, the control itself checks if its output is found in the cache, and if so the Render method will just write the cached output. If it is not found in the cache, the PreRender method will run the Render method normally and capture the output and store it in the cache.
In your case you would of course need a bit more logic which would check the relevant property on the control and use that to check if a cached version exists.
Disclaimer: This is an extremely simple test control. I have not tried to figure out how to make all of this work with controls that contain event handlers etc. So take it for what it's worth...
i'm a beginner in .NET, and search since yesterday morning to resolve my problem without finding the solution.
Here is my problem :
I create dynamically some User Controls by this way, because I need to give parameters :
List<ANNOUNCEMENT> listAnnouncement = getAnnoucements();
foreach(ANNOUNCEMENT ann in listAnnouncement)
{
if(ann.IS_CURRENT_ANNOUNCEMENT && currentAnnouncement == null)
{
currentAnnouncement = ann;
}
List<Object> listParams = new List<Object>();
listParams.Add(ann);
AnnouncementPresentation ap = (AnnouncementPresentation)(Controller.LoadControl(Page, "~/UserControls/AnnouncementPresentation.ascx", listParams.ToArray()));
/* important for the end of the method */
ap.modifyAnnouncementButtonClick += new EventHandler(modifyAnnouncementButtonClick);
pnl_announcements.Controls.Add(ap);
}
In this ASCX, I have a button, and when user will click on it, I want to call a method contained in my ASPX, so I do this in the ASCX :
public event EventHandler modifyAnnouncementButtonClick;
protected void btn_modify_announcement_Click(object sender, EventArgs e)
{
PageAdminAnnonces.currentAnnouncement = annonce;
modifyAnnouncementButtonClick(sender, e);
}
And this in the ASPX :
protected void modifyAnnouncementButtonClick(object sender, EventArgs e)
{
initListOfAnnouncement();
lbl_errors.Text = currentAnnouncement.TITLE;
}
I think everything works, but there is the problem : It works once, and at the end of the method, I delete my ASCX as you can see, and create new ASCX. But they don't have the methods, and when I click again, nothing works, so the ASPX is reloaded. After reloading, it works again.
Do i do something wrong?
According to the information in the comments, I suppose that your solution does not work because you are recreating the controls in the Click event handling method, which is very late in the page's lifecycle and should not be used for adding controls.
As mentioned in the comments, I suggest you to create the controls in Page_Init or Page_Load and not recreate them in the button's Click handling method. You should also assign a unique ID to each of them. Then, in the Click handler, you can use FindControl method to acces the created controls. Alternatively you can just save the references to the controls upon creation, so you can access them later easily.
Useful links:
http://msdn.microsoft.com/en-us/library/ms178472.aspx
http://visualstudiomagazine.com/articles/2010/10/11/more-on-adding-controls-dynamically.aspx
We are rendering usercontrols dynamically like this:
public string RenderControl(string pathcontrol)
{
string html;
var page = new Page();
var control = page.LoadControl(path);
page.Controls.Add(control);
// do stuff to the control (give it some data to work on)
using (var writer = new StringWriter())
{
HttpContext.Current.Server.Execute(page, writer, false);
html = writer.ToString();
}
return html;
}
This lets us the same user controls when rendering pages normally as we do when rendering responses to ajax calls. However, when adding controls which themselves contain a scriptmanagerProxy we run into the problem that the newed up Page object doesn't contain either a ScriptManager or the HtmlForm in which the ScriptManager needs to run.
Is there any way around this?
Yours
Andreas
As others have said you can add a ScriptManger dynamically easily enough [ Add ScriptManager to Page Programmatically? if your Page object is complete.
Can you try using BuildManager.CreateInstanceFromVirtualPath() to create the Page object instead? You issue may be how you create that object. There's a bit more to creating a new page than newing up the Page object.
Eg.
Page page
= BuildManager.CreateInstanceFromVirtualPath("~/Test.aspx", typeof(Page))
See also http://www.west-wind.com/weblog/posts/120530.aspx for a little more background.
Can you do something like this:
page.Form.Controls.AddAt(0, New ScriptManager())
Edit: I think you'd also need to add your control to the page's form, not just to the page itself, right? It's my understanding that the form is created with the page, but if not you should be able to just do:
page.Form = new HtmlForm()
You may also need to do something like:
page.Controls.Add(page.Form)
Sure, the trick is to add it in a page's Init event handler. You can use:
Page.Init += delegate {
// check for script manager
if( ScriptManager.GetCurrent(Page) == null ) {
ScriptManager m = new ScriptManager();
m.ScriptMode = ScriptMode.Release;
Page.Form.Controls.AddAt(0, m);
}
}
I'd recommend avoiding dynamically adding forms to your page if you can. For example, the above code snippet assumes a form is already present on the page.
Update
Sure, thanks for pointing that out Andreas. Here's an update. So, there is no setter for Page.Form - but you are correct in that you can add a new HtmlForm to the Controls collection. Once added, the Page.Form property is no longer null. That will allow you to add the ScriptManager dynamically as seen above. Here is a code sample that shows this working (ASPX file is a simple page without a server side form):
public partial class Pages_Test_DynamicFormSample : Page {
protected void Page_Init(object sender, EventArgs e) {
Controls.Add( new HtmlForm() );
ScriptManager m = new ScriptManager();
m.ScriptMode = ScriptMode.Release;
Form.Controls.AddAt(0, m);
}
protected void Page_Load(object sender, EventArgs e) {
// ScriptManager test
var t1 = new System.Web.UI.WebControls.TextBox();
var t2 = new System.Web.UI.WebControls.TextBox();
Form.Controls.Add( t1 );
Form.Controls.Add( t2 );
ScriptManager.GetCurrent(Page).SetFocus( t2 );
}
}
Enjoy - btw, setting the ScriptManager's ScriptMode to Release obviously isn't required. We do it just to avoid some JavaScript bugs found in the Debug version of the ASP.NET script runtime.
I've got a rather lengthy question I'm afraid. I'm fairly new to ASP.NET so please bear with me.
I have built a control for an ASP.NET page that lists a number of options. Each option has two clickable areas (call them buttons for the sake of simplicity). One to select the option and one to hide the option.
protected void Page_Load(object sender, EventArgs e)
{
RenderOptions();
}
public void RenderOptions()
{
for (int i = 0; i < 5; i++) {
HtmlGenericControl div1 = new HtmlGenericControl("div");
div1.Attributes.Add("onclick", ClientScript.GetPostBackEventReference(this, "option" + i));
m_TreeContainer.Controls.Add(div1);
HtmlGenericControl div2 = new HtmlGenericControl("div");
div2.Attributes.Add("onclick", ClientScript.GetPostBackEventReference(this, "option" + i));
m_TreeContainer.Controls.Add(div2);
}
}
public void RaisePostBackEvent(string arg)
{
//do something
}
This works fine (I do implement the IPostBackEventHandler interface). The problem here is that there doesn't seem to be a way for me to find which HTML element was clicked and thus which action should be performed in the RaisePostBackEvent method.
What I tried to do is create a new class (HtmlDivControl) which looks like this:
class HtmlDivControl : HtmlGenericControl, IPostBackEventHandler
{
#region Delegates
public delegate void ClickEventHandler(object sender, string eventArgument);
#endregion
#region Properties
private ClickEventHandler m_Click;
public ClickEventHandler Click
{
get { return m_Click; }
set { m_Click = value; }
}
#endregion
#region Constructors
public HtmlDivControl()
{
}
#endregion
public void RaisePostBackEvent(string eventArgument)
{
m_Click.Invoke(this, eventArgument);
}
}
Now I made div1 and div2 my HtmlDivControl rather than HtmlGenericControl, set the Click property to a method (delegate) and passed the div (div1 or div2) itself as control for the GetPostBackEventReference method. This time, I could not only differentiate between the divs but also pre-determine the action that should be performed. However, the RaisePostBackEvent for controls are called after PageLoad. So the problem I'm with now is that the whole options control is rendered before the events are handled (and thus, an option that should for instance be hidden isn't because the actual hiding happens after the rendering). Moving the RenderOptions() call to the PageLoadComplete method doesn't help either, since then the div controls won't exist yet.
I'm pretty sure I'm missing something quite fundamental here. But could someone please explain me how I should approach something like this?
p.s.
How am I supposed to write underscores here? They're used to make text italic? Is there some escape character?
For someone new to ASP.Net, you've done pretty well so far. Your roadblock here is actually the way you are thinking about the issue. You should get a good grasp of the ASP.Net Page Lifecycle - you are missing something very fundamental.
In a nutshell, you want your page to rebuild it's state to the same way it was before the postback. Then process your events. Then make any state changes.
You're thinking about it as if your html controls should know about their state change at the start of the request, which is incorrect. There has to be the rebuilding phase first. This is critical for ASP.Net to even figure out which events to raise.
What I would recommend:
move your "RenderOptions()" method to the Page_Init handler. This will save you lots of issues if you ever incorporate ViewState into your controls. (I would also rename it, as it's not truly rendering anything, it's just adding your controls to the page. Render has a specific context in ASP.Net).
Then, in your OnClick event handlers for your controls, simply set your controls visibility as necessary, rather than trying to control the way they are rendered. It is always much simpler to set controls to Visible=False rather than try to change the way the controls are being rendered to the page. Remember that if you set Visible=False, there will be zero html sent to the response for that control, but the server will still know it's on the page, so you can still deal with it.
Think about your event handlers as the place where you will change the state of the page. It's where your logic should be in this case, rather than in Page_Load.
How to display the message Box within the Content Page..?
After updating profile..I want to display a Message Box in content page..
Please give your suggestions.. Thanks in advance.
You could use the Page.RegisterStartupScript method.
if (UpdateProfile())
Page.RegisterStartupScript("startup", "<script>alert('your profile has been updated..');</script>");
Assuming of course that UpdateProfile() does the work and returns a boolean indicating success :)
Alternatively (because that method is obsolete), you could use the ClientScriptManager.RegisterStartupScript method instead.
if (UpdateProfile())
Page.ClientScript.RegisterStartupScript(this.GetType(), "startup", "<script>alert('your profile has been updated..');</script>", false);
write this method first
public void MsgBox(String ex, Page pg,Object obj)
{
string s = "<SCRIPT language='javascript'>alert('" + ex.Replace("\r\n", "\\n").Replace("'", "") + "'); </SCRIPT>";
Type cstype = obj.GetType();
ClientScriptManager cs = pg.ClientScript;
cs.RegisterClientScriptBlock(cstype, s, s.ToString());
}
after whenever you need message box just follow this line
MsgBox("Your Message!!!", this.Page, this);
The error you are seeing is caused by your content page somehow trying to inject the javascript to create the alert box outside of the Content control.
One way of doing this that should work is to inject the javascript at the master page level.
To do this expose a method in you master page code behing like the following:
public void ShowAlertMessage(String message)
{
string alertScript = String.Format("<Script Language='javascript'> alert('{0}');</script>", message);
Page.ClientScript.RegisterStartupScript(this.GetType(), "Key", alertScript, false);
}
Then, from the content page you can call this method on the Master object:
protected void UpdateProfile_Click(object sender, EventArgs e)
{
YourMasterPage master = (YourMasterPage) Master;
master.ShowMessage("Profile updated.");
}
This method also has the nice benefit of encapsulating your MessageBox logic for all your content pages.
One caveat on the above is that I can't for the life of me reproduce the error you are seeing, I've tried every combination of master/content markup I can think of and can't get the error. Any of the other examples provided here in the other answers work happily for me.
Response.Write("[script] alert('message here');[/script]");
stackoverflow won't allow the real tags replace the [ with < and the ] with >