is there a way to find all script files added to a page in asp.net code behind? i am trying to add script dynamically but would like to check first if it already exist on the page.
AFAIK, no. Other developers can just add <script> tag on the fly and not through the .NET objects.
If you ensure that everyone uses ScriptManager, then you can use GetRegistered* methods on the object.
If it's inline script, you can use ClientScriptManager.RegisterClientScriptBlock which uniquely identifies a script by its type and key and will make sure it's registered only once.
Related
I am utilizing controls in my asp.net application. I have a register tag the source of which needs to be dynamic. I am using the line below which functions correctly when the full path is specified but when I change it to the variable I get a parser error. Any idea how I can go about doing this?
Thanks
It might be better to use Load Control from the code behind of the aspx page.
If I'm understanding you correctly — you can't use a variable in those directives (Page, Register, etc). They have to be constant expressions.
However, it is possible to dynamically load ASCX controls. You would have to do this in code, though, and it would not involve the Register tag.
I'm currently working on an ASP.NET 3.5 project, and I wanted to know your opinion regarding the following situation, which I happen to run into sometimes:
Let's say I've defined the following control of an imaginary component framework somewhere in my code:
<Window runat="server" ID="windowTest" />
Let's assume that with the above mentioned imaginary component framework it's possible to get a reference to my Window control from the client-side using its ID (for example to change its appearance):
function MyFunc(){
var win = GetWindow("windowTest");
}
Let's also assume that both code snippets are placed in different files, e.g. the JavaScript code in MasterPage.Master and the control in AnotherPage.aspx.
As you might already have noticed, the passing of the control's ID as a hard-coded string to the GetWindow function is a bit problematic here, since changing the control's ID is going to break the JavaScript function.
This situation surely smells like it needs a good ol' Replace Magic Number with Symbolic Constant refactoring. I can achieve this by dynamically creating the Window control and using a constant for the value of the control's ID:
AnotherPage.aspx:
Window windowTest = new Window();
windowTest.ID = Consts.ID_WINDOW_TEST;
form1.Controls.Add(windowTest);
MasterPage.Master:
function MyFunc(){
var win = GetWindow("<%= My.Namespace.Consts.ID_WINDOW_TEST %>")
}
My question now is: How do you handle such situations? Do you create all your controls dynamically (like shown in the example above) when running into this situation, and are there any drawbacks using this approach, e.g. Designer doesn't display the control anymore? Or do you say "Screw it, nobody's going to change that control's ID" and leave it hard-coded in your code? Or do you have other approaches to this situation?
I personally am a fan of the of the first option (refactoring), since a) it makes sure that a change to the ID is not going to break my code and b) I almost never work with the Designer, but I thought I'd ask this question on SO to get some valuable opinions on this.
Thanks in advance for all the responses.
Greetings,
Giu
Update / Clarification:
I made a small error in the first version of this question by stating that the code snippets are placed in the same file. Since both the control and the JavaScript method are located in the same file, there is no need to create the control dynamically and defining the control's ID using a constant; by defining the control directly in the .aspx file I could use its ID in the JavaScript method as follows: GetWindow("<%= windowTest.ID %>");
But, my problem is another one; the control and the JavaScript method are each placed in different files, in which case the mentioned approach of using the control's ID doesn't work anymore. Therefore I introduced the solution mentioned in my question with the constant and the dynamic creation of the control. I now corrected both the filenames in my question so that the correct scenario is described to which my question is related.
In 4.0 you can control the client ID that's generated in master/content page situations quite well. but i believe if someone changes the ID manually in the page at one place and not in the javascript code it will still be a problem. If you are the only one who'll be working on this code then you can always be mindful and refactor properly. Otherwise you can go in for the constants option or store the IDs in a separate resource file.
In my opionion there a two suitable solutions:
1) Use the JQuery framework to get ahold of the html element you want to adress via JavaScript. JQuery is designed to be able to work with autogenerated hierarchically created control IDs
2) Use .net Framework 4.0 and don't use autogeneration of the Control ID. (I've heard that this is a new feature in 4.0. I think in your situation it might be worth trying out)
Check out Rick Strahl's blog post entitled "A generic way to find ASP.NET ClientIDs with jQuery"... it seems to have some good ideas that could be of some help to you.
He uses jQuery, as the first responder suggested, but does it in a way that you are using ASP.NET's built-in ClientID property to get the actual id ASP.NET generates and uses a client-side friendly mechanism that enables you to write script code referencing controls that won't break with ID changes.
I think I summed up the question in the title. Here is some further elaboration...
I have a web user control that is used in multiple places, sometimes more than once on a given page.
The web user control has a specific set of JavaScript functions (mostly jQuery code) that are containted within *.js files and automatically inserted into page headers.
However, when I want to use the control more than once on a page, the *.js files are included 'n' number of times and, rightly so, the browser gets confused as to which control it's meant to be executing which function on.
What do I need to do in order to resolve this problem? I've been staring at this all day and I'm at a loss.
All comments greatly appreciated.
Jason
If the issue is simply that the same file is being embedded multiple times and causing conflict, look into using RegisterClientScriptInclude. If you use the same identifier for all of your calls to RegisterClientScriptInclude only one instance of that file will be embedded:
http://msdn.microsoft.com/en-us/library/2552td66.aspx
However, if the issue is that your methods are being called but they don't know what controls on the page to operate on then you need to figure out how to provide your JS some context. Define a JavaScript object that represents your control on the client-side, and on the server-side emit the call that will instantiate it with the client IDs of the controls you'll be operating on.
We are using CustomValidator to validate User Control. The control works fine until you drop two instances of the Control on the same page, since they reference the exact same JavaScript functions, only one control works. Work around, we appended JavaScript function name with control id.
Validate_SAPDepartment<% =ControlId %>(oSrc, args) {...}
In codebehind, we assinged ClientValidationFunction
CustomValidator1.ClientValidationFunction = "Validate_SAPDepartment" + this.ControlId
This may not be the right approach but it works.
I've had this situation before. You register a separate JavaScript file with the page using the ScriptManager. You can stream this as a resource file embedded into the dll if you wish.
Then you only call into the functions from your control.
Otherwise a completely separate jquery file may also work.
I was wondering if its possible to have an ASP.NET AJAX custom usercontrol 'register' its use of CSS files like it does with JS files. ?
Eg: Implementing the IScriptControl interface allows for the GetScriptReferences() to be called by the Script Manager, is there a similar thing for CSS files?
No.
You could write your own methods to use embedded resources and generate html to write them to the page.
As a best-practice approach, though, I wouldn't recommend this. You should have a clear separation of style and markup. If you want to write a custom control that is dependent on a stylesheet, then I suggest that you provide a default css file along with your control.
EDIT (to answer questions in the comments)
You can run this code to add a reference to the CSS file to your page (at runtime). Note that because you're using the RegisterClientScriptBlock method, you can manage insert duplication. Here is an excerpt from the link for the method:
A client script is uniquely identified by its key and its type. Scripts with the same key and type are considered duplicates. Only one script with a given type and key pair can be registered with the page. Attempting to register a script that is already registered does not create a duplicate of the script.
StringBuilder sb = new StringBuilder();
sb.Append(#"<link rel=""stylesheet"" type=""text/css"" href=""");
sb.Append(this.Page.ClientScript.GetWebResourceUrl(this.GetType(), resourceName));
sb.Append(#""" />");
this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "MyCSS", sb.ToString());
I am trying to make use of the yahoo exceptional performance rule : avoiding duplicate script
To do so i would like to be able to know whether or not a script was already added to the page before injecting it in the page. It looks like i can't figure what has been added in asp.net code behind unless i have a scriptmanager added to the page. but i would like to avoid using asp.net AJAX. From the description of the rule, it looks like it is something possible in php though.
Assuming that i can't do the check in my code behind, i was considering using jQuery $.getString function but it doesn't check before fetching the script. If i was to choose the javascript file, would i have to parse the whole http response in order to figure out which script was loaded on the page?
If the page is registering the scripts with the ASP.NET Page.ClientScript Register APIs then you can use Page.ClientScript.IsClientScriptIncludeRegistered. On the other hand, if you are using those APIs you don't really need to call it, since it already ensures only one of each is registered.
http://msdn.microsoft.com/en/us/library/system.web.ui.clientscriptmanager.isclientscriptincluderegistered.aspx
If the page just has regular ole script elements statically in the markup, and you need to detect if a script is loaded on the client side, you will have to get all the script elements on the page and look at their .src values. The thing with that is that some browsers automatically resolve that url to a full path, not just the one you declared. So, you can account for that in various ways -- you can just search for the end of the string being the script you want, or you can cause the url you want to compare with to also be resolved by setting it onto a dynamically created script element (which you never add to the DOM but is still resolved for you).
This is just off the top of my head, sorry if I get something wrong:
var s = document.createElement("script");
s.src = "foo.js";
var loaded, scripts = document.getElementsByTagName("script");
for (var i = 0; i < scripts.length; i++) {
if (scripts[i].src === s.src) {
loaded = true;
break;
}
}
if (loaded) {
// this script is already loaded
// assuming you dont have multiple copies in different locations
}
You don't need to use any client-side scripting to do this... you can do this in your code behind using the ClientScriptManager without needing to make use of ASP.NET AJAX (I think you're confusing ClientScriptManager with ScriptManager*) in your control/page just use:
ClientScript.RegisterClientScriptInclude("some-script", "myScript.js");
or from your user controls:
Page.ClientScript.RegisterClientScriptInclude("some-script", "myScript.js");
This will use the key "some-script" & only register one copy of the script on the page.
*To be clear I think the confusion is arrising from the difference between these:
ClientScriptManager if a server-side helper class which is used to manage client side scripts (in other words its whole purpose is to do exactly what you are trying to do). It is accessed via the Page's ClientScript property.
ScriptManager is a Control used to aid client side Ajax scripting in ASP.NET AJAX
(hell I even confused myself & gave the wrong example code initially)
well that wouldn't actually work in a master detail scenario with multiple web user controls.
Then you wouldn't have control over who has to do the script initialization if the web user control is dynamic.
It's easier to link once, but a developer would have to weigh his options between ClientManager and using a script load.
yeah you have to parse the whole response...
why don't you create a javascript file and put all of your javascript there and then import that javascript file in your code??? in this way you can get rid of duplicate script insertion.