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Cancel Postback Using ImageButton: The Sequel

I am trying to build a toolbar. To do so, I am exploring using multiple asp:ImageButtons to build the bar.

I have been able to get around the problem of being able to execute code that I want to use on the client side (although I admit that the ImageButton is really intended to execute code on the server).

I have also reviewed comments about this identical issue that previously appeared in this forum. See:

http://www.experts-exchange.com/Programming/Programming_Languages/Dot_Net/ASP_DOT_NET/Q_21125076.html?query=postback+ImageButton&topics=865

The conclusion at that time was to use the standard html image control.

However, the basic image control does not have tooltips or even a click event.

The issue I have with the ImageButton is that after I have executed my code locally, it wants to do a postback. I suppose if I could set an attribute like AutoPostBack="false", everything would be fine.. But the ImageButton doesn't have the AutoPostBack option.

Preventing a postback is important to me because if I were to change a button from an "enabled" to a "disabled" image, pressing any other button on the bar refreshes the bar back to its original default images - as the postback reloads the entire page.

I'd like to minimize the work required to preserve the current status of the buttons, and eliminate unnecessary postbacks whenever possible.

Any thoughts?



 


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gbmcneil
Asked:
gbmcneil
1 Solution
 
CJ_SCommented:
Programmatically you can do so by:
instance.Attributes.Add("onclick", "return false;")

The key is that the onclick returns false. So it needs to render like:
<input type="image" onclick="yourclientfunctions();return false;" />



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nitrogenxCommented:
<a href="#" onclick="javascript"><img src="url" alt="Tooltip Text" /></a>
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gbmcneilAuthor Commented:
I guess my question is: "Is it possible to use an asp control like asp:ImageButton and execute a function on the client-side without triggering a postback?"

You are telling me to use <input type="image"  blah blah blah...  because it gives me access to local, client-side code with the onclick attribute. This is an improvement because I must admit that I mistakenly assumed that the standard image control (the <img tag) was being referred to in the original postback question.

But, I've still got to build my own tooltips. I can do it. No big deal. But, can I simply cancel the postback? Then I can have my tooltips (or whatever functionality might be built into a particular "asp" control) without refreshing the whole page.
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CJ_SCommented:
What you can do to keep the functionality is by adding some additional code automatically. You can create a new component, reference it from the .aspx and use it like you normally would

Imports System
Imports System.Web

Namespace YourNamespace
 Public Class ExtendedImageButton
   Inherits System.Web.UI.WebControls.ImageButton

  Protected Overrides Sub OnInit(ByVal e as System.EventArgs)
    MyBase.OnInit(e)
    EnsureChildControls()
    Attributes.Add("onclick", "return false;")
  End Sub
 End Class

Save the page in the root of your website with the filename ExtendedImageButton.vb, and compile with
vbc /t:library /out:bin\yournamespace.dll /r:system.dll /r:system.web.dll extendedimagebutton.vb

Now add a register statement to the top of the page AFTER the @ Page directive:
<%@ Register TagPrefix="yourcontrols" Namespace="YourNamespace" Assembly="YourNamespace" %>

Now whenever you need to have access to your ImageButton you use the ExtendedImageButton  instead. Add it to your page with:
<yourcontrols:ExtendedImageButton id="yourid" ... allyourotherproperties ... runat="server" />

Use the object the way you would normally.

CJ.

(code not tested, I assume it will work though)
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gbmcneilAuthor Commented:
Gosh. I would never have figured this one out without your help.

Thanks very much. Give me a little time to try this out.
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Justice777Commented:
Or, if you dont want to have 2 separate controls, just add "return false" in the OnClientClick property of the control, or to the end of that property ";return false" if you already have something in it.
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