How to programmatically create a <script> tag and a script inside an ASP.NET page?

Question

From time to time I run into situation in which I could solve a given problem by dynamicly creating piece of JavaScript, spesific to that instance of the page, that I could then insert in the final markup. Usualy this is because I want some behaviour to happen on the client side, rather than on the server side and creating a static JavaScript isn't an option.
For example, when trying to submit a files original path without submitting the file itself, when trying to do it for multiple dynamicly created components.

How would you recommend me to create a script tag and populate it with, for example, JavaScript?

Do you want your script tag inside the <head> block or anywhere in the <form runat=server> block? — Philippe
– Philippe, Commented Mar 24, 2009 at 13:02
@Philippe: I do belive anywhere inside the <form> tag would do fine. Of course, someone else might appriciate a solution for the <head> tag as well. — vipirtti
– vipirtti, Commented Mar 24, 2009 at 13:12

Joel Coehoorn · Accepted Answer · 2009-03-24 13:01:21Z

8

Use your page's ClientScriptManager and it's RegisterClientScriptBlock() method.

string javascript = "javascript goes here"; 
string scriptname = "Name of this script"; // used to prevent adding the same script twice at two places in the page life cycle
if (!Page.ClientScript.IsClientScriptBlockRegistered(scriptname)) 
{ 
    Page.ClientScript.RegisterClientScriptBlock(this.Page.GetType(), scriptname, javascript, true); 
}

answered Mar 24, 2009 at 13:01

Joel Coehoorn

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4 Comments

Philippe Over a year ago

Writing javascript in code-behind is a bad practice. When you need to tweak or change the behavior of UI, you need to recompile all the project.

Joel Coehoorn Over a year ago

Good point. Even better if you can do this using RegisterClientScriptInclude

Philippe Over a year ago

I misunderstood the original question. I voted up your answer. I'll check for RegisterClientScriptInclude when needed, thanks alot!

Joel Coehoorn Over a year ago

You could also create an HttpHandler (*.ashx) file to spit out the javascript, and just use a normal script tag in your markup that points to that handler.

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