UserControl Self-Inserting JavaScript

[Alex Maghen]

I am building an ASP.NET UserControl. The UserControl will be making use of
one or two JavaScript functions. I want to assure that those functions will
be on the Page once and only once, but I don't want to have to remember to
insert the JavaScript on the page itself.

Instead, I want the UserControl to basically do this: Each time the
UserConrtol starts (PreRender? I'm not sure), I want it to check if a
JavaScript clock is loaded into the containing Page. If it is already there,
the control does nothing and just continues. If it's *not* there, it inserts
the JavaScript block itself.

This way, we're sure that the JavaScrip will be there if the control is
there, but we don't have to worry about it appearing on the page more than
once.

I think I should be using the
Page.ClientScript.IsClientScriptBlockRegistered()
function and also
Page.ClientScript.RegisterClientScriptInclude()

but I'm not sure how and I'm not sure where in the life-cycle of the
UserControl, this stuff can be tested and altered.

Any help, or even code-samples are much appreciated!

Alex

 

[Vince Xu [MSFT]]

Hello Alex,


I suggest you use the code as below:

if (!ClientScript.IsStartupScriptRegistered(this.GetType(),
"test"))
{
ClientScript.RegisterStartupScript(this.GetType(), "test",
str.ToString(), true);
}

It will check if you have registered the script to the page. If not, it
will register the script. Please put them in Page_PreRender event.

RegisterStartupScript will be render to the area which is below the "form"
on the page client.
RegisterClientScriptBlock will be render to the area which is above the
"form" and "body" on the page client.

Sincerely,

Vince Xu

Microsoft Online Support


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--------------------
| Thread-Topic: UserControl Self-Inserting JavaScript
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| From: =?Utf-8?B?QWxleCBNYWdoZW4=?= <[email protected]>
| Subject: UserControl Self-Inserting JavaScript
| Date: Mon, 29 Jun 2009 18:34:01 -0700
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|
| I am building an ASP.NET UserControl. The UserControl will be making use
of
| one or two JavaScript functions. I want to assure that those functions
will
| be on the Page once and only once, but I don't want to have to remember
to
| insert the JavaScript on the page itself.
|
| Instead, I want the UserControl to basically do this: Each time the
| UserConrtol starts (PreRender? I'm not sure), I want it to check if a
| JavaScript clock is loaded into the containing Page. If it is already
there,
| the control does nothing and just continues. If it's *not* there, it
inserts
| the JavaScript block itself.
|
| This way, we're sure that the JavaScrip will be there if the control is
| there, but we don't have to worry about it appearing on the page more
than
| once.
|
| I think I should be using the
| Page.ClientScript.IsClientScriptBlockRegistered()
| function and also
| Page.ClientScript.RegisterClientScriptInclude()
|
| but I'm not sure how and I'm not sure where in the life-cycle of the
| UserControl, this stuff can be tested and altered.
|
| Any help, or even code-samples are much appreciated!
|
| Alex
|

 

[Mythran]

Hello Alex,


I suggest you use the code as below:

if (!ClientScript.IsStartupScriptRegistered(this.GetType(),
"test"))
{
ClientScript.RegisterStartupScript(this.GetType(), "test",
str.ToString(), true);
}

It will check if you have registered the script to the page. If not, it
will register the script. Please put them in Page_PreRender event.

RegisterStartupScript will be render to the area which is below the "form"
on the page client.
RegisterClientScriptBlock will be render to the area which is above the
"form" and "body" on the page client.

Sincerely,

Vince Xu

Microsoft Online Support

I thought RegisterStartupScript performs the IsStartupScriptRegistered check
so you don't have to call it yourself?

Mythran

 

[Vince Xu [MSFT]]

Hello Mythran,
Yes, you're right. As you said, RegisterClientScriptBlock and
RegisterStartupScript will do check if the current key has been registered.
If the current key is exist in list, it will return the related value
instead of setting the new value the user registered.
According to the MSDN document, we suggest developer use
IsStartupScriptRegistered/IsClientScriptBlockRegistered to check if it has
been registered before RegisterClientScriptBlock/RegisterStartupScript.
http://msdn.microsoft.com/en-us/library/system.web.ui.page.registerstartupsc
ript.aspx

Because in this way, we can prevent executing the superfluous code which is
in the if block.


Regards,

Vince Xu

Microsoft Online Support


--------------------
| From: "Mythran" <[email protected]>
| References: <[email protected]>
<I0JFFNT#[email protected]>
| In-Reply-To: <I0JFFNT#[email protected]>
| Subject: Re: UserControl Self-Inserting JavaScript
| Date: Tue, 30 Jun 2009 08:38:53 -0700
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|
| | > Hello Alex,
| >
| >
| > I suggest you use the code as below:
| >
| > if (!ClientScript.IsStartupScriptRegistered(this.GetType(),
| > "test"))
| > {
| > ClientScript.RegisterStartupScript(this.GetType(),
"test",
| > str.ToString(), true);
| > }
| >
| > It will check if you have registered the script to the page. If not, it
| > will register the script. Please put them in Page_PreRender event.
| >
| > RegisterStartupScript will be render to the area which is below the
"form"
| > on the page client.
| > RegisterClientScriptBlock will be render to the area which is above the
| > "form" and "body" on the page client.
| >
| > Sincerely,
| >
| > Vince Xu
| >
| > Microsoft Online Support
| >
| >
|
| I thought RegisterStartupScript performs the IsStartupScriptRegistered
check
| so you don't have to call it yourself?
|
| Mythran
|
|
|

 

[Alex Maghen]

I have two more questions about this:
1. How efficient is IsClientScriptBlockRegistered()? If I have 50 of a
control on a page and each instantiation of that control performs this
IsClientScriptBlockRegistered(), is this a heavy process? It doesn't require
parsing the page each time, right? If it's just a lookup in a collection
that's already been built than I imagine it's cheap. I just don't want to do
something very heavy 50 times for every single time the page is generated.

2. Is there a way to do this some procedure of checking whether the script
is present in the page, but using RegisterClientScriptInclude() instead? It's
cleaner for me if I can use an instruction to load the JS from file, but I
can't find something like "IsClientScriptIncludeRegistered()". How can I do
this?

Thanks.

Alex

 

[Vince Xu [MSFT]]

Hello Alex,

1. IsClientScriptBlockRegistered will check the collection list that's
already been built according to the "key" registered. It's fine to loop 50
times I think if there are not too much items in the collection list.

2. Actually, you can use IsClientScriptIncludeRegistered to check the
collection list that's already been built by RegisterClientScriptInclude.--
Page.ClientScript.IsClientScriptIncludeRegistered

Sincerely,

Vince Xu

Microsoft Online Support