programatically updating a panel using onblur

Ok, this is driving me nuts and I can't believe there's not a way to do this.

Basically I have a user control that dynamically adds text boxes to its control tree at runtime. I have an UpdatePanel control sitting in the top of my user control with a button and a literal control. When the button is clicked it calls a buttonclicked method in the user control that sets the literal to some text and calls the update method on the panel. It all does what it's supposed to do when I click the button and AJAX works just fine.

Now here's the problem, how on Earth do I add an onblur event to the dynamically created text boxes that will either

a) update the panel; or

b) call the buttonclicked method directly; or

c) click the button

I've tried

1txtBox.Attributes.Add("onblur","javascript:__doPostBack('ctl00_contentPlaceHolder_quoteControl_quoteButton','OnClick','');");

And a large number of variations on the above but to no avail. The problem with the above is that I don't necessarily know the full id of the button control at compile time (and even if I did I really, REALLY wouldn't want to hard code it in my class) and if it doesn't find the control then it does a full form postback making the update panel redundant. I understand that I cannot wire in a custom event handler directly to the onblur method (like you can for the text changed) so it has to be client side.

Is there a way to trigger server side events through client side script? I have to get this done even if it involves hand rolling some javascript function that I can call from the onblur attribute to call the event.

I'm a back end business tier coder so any help with the client side would be most gratefully appreciated.

Rick Edwards

Ok, I've discovered a nasty way to do this using the event hi-jacking technique or "hidden button" method found here:

http://www.dotnetjohn.com/articles.aspx?articleid=224

I'd originally shy'd away from this as it's blatantly a hack but having now spent two day researching this I can't find another way of doing it.

Basically I add a hidden button to my update panel on the parent control and wire in the button click method on the parent control code behind. I then raise the event handler in the parent user control and pass this to the child control classes that are part of my control factory. When a textbox control is manufactured by the factory I can then add the oblur attribute and wire in the button click event handler. The button click method is initialised in the parent user control and within it I call the update method for the AJAX panel.

This is great for just updating a single panel from multiple onblur events, the problem now occurs if I want to update different panels from different textbox controls, I suddenly have to start adding hidden buttons all over the place so this is far from an ideal answer.

I've just found an article on asynchronous callback features in .NET2 and it looks like I might be able to roll my own textbox control with an onblur method built in, anyone with any experience of this?

Rick Edwards

Sorry if I'm missing something, but why couldn't you just set AutoPostBack="true" on the TextBox?

Firstly the autopostback event is fired on either tabbing out of the textbox or on pressing enter and not necessarily on loss of focus. Also I don't want to fire a postback event, I actually need to fire a custom event that calls the update method on my update panel and therefore run an asynchronous postback and a partial render. I don't want to rerender the entire form.

Hope that makes sense. I tried the autopostback initially thinking along your lines but it couldn't do what I wanted.

Rick Edwards

Yes, you would be limited to whenever AutoPostBack actually fires. But then it will do an async postback (as long as it's in your UpdatePanel or set as a trigger) and run whatever handler you've set in OnTextChanged. It shouldn't reload the entire page.

If AutoPostBack doesn't do what you want, your hidden button method should work, but I'd use MyButton.ClientID to get the ID so you don't have to hardcode it (which as you said is error-prone).