ScriptManager.RegisterStartupScript Saves adding script blocks several times

Question

I have a timer update panel configured to automatically check for data updates every minute or so.

If he sees that data updates, he is configured to invoke a local script with serialized JSON data.

ScriptManager.RegisterStartupScript(UpdateField, GetType(HiddenField), ACTION_CheckHistoryVersion, "updateData(" & data & ");", True) 

where "data" might look something like

 { "someProperty":"foo", "someOtherProperty":"bar", "someList":[ {"prop1":"value"}, {"prop2":"value"}, ... ], "someOtherList":[{},...,{}] } 

"data" can be quite large, and sometimes only a few elements change.

I'm having a problem. Each time I send this back to the client, it is added as a new script block, and existing blocks are not deleted or replaced.

the output looks something like this:

 <script type="text/javascript"> updateData({ "someProperty":"foo", "someOtherProperty":"bar", "someList":[ {"prop1":"value"}, {"prop2":"value"}, ... ], "someOtherList":[{},...,{}] }); </script> <script type="text/javascript"> updateData({ "someProperty":"foo", "someOtherProperty":"bar", "someList":[ {"prop1":"changed"}, {"prop2":"val"}, ... ], "someOtherList":[{},...,{}] }); </script> <script type="text/javascript"> updateData({ "someProperty":"foos", "someOtherProperty":"ball", "someList":[ {"prop1":"changed"}, {"prop2":"val"}, ... ] }); </script> 

with a new script block created each time a data change occurs.

Over time, the amount of data accumulating in the browser can become potentially huge if we just add it, and I can’t imagine how most browser users will do it, but I don’t think it could be good.

Does anyone know if there is a way to simply replace the code that was sent back to the browser and not constantly add it like that?

Answer 1

I would recommend using a web service with some web method that you will call inside window.setInterval. In a successful handler of your web method (client side), you can simply take the answer and do whatever you want with it. And it will not be saved on your page (well, if you do everything wrong). The advantage is that you minimize the size of the request (the updatepanel will transfer all your data in the view), which can be quite large) and limit the use of server resources (the update panel causes the entire page life cycle, presumably slightly changed, but in any case - all these page_load, page_init, etc.), and using the web service you will be just what you need.

Here is an article in which you can see how it could be created and used on the client side. Looks good.

Answer 2

I came up with a hack that seems to work in my situation.

I use jQuery to find the script tag that I create and delete it after calling it.

Here is an example:

First I create guid:

 Dim guidText as string = GUID.NewGuid().ToString() 

I am creating a function similar to the following:

 function RemoveThisScript(guid){ $("script").each(function(){ var _this = $(this); if(_this.html().indexOf(guid)>-1) _this.remove(); }); } 

Then I add the following code to my output line:

 ... & " RemoveThisScript('" & guidText & "');" 

This causes jQuery to look at all the scripts on the page that have a GUID (essentially the calling function) and remove it from the DOM.