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ds869

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'Enter key pressed' event, form submit, Page_Load, __postback in .NET

Hi,

I am using C#.NET to create some simple web pages. I noticed that 'enter_key_pressed' (window.event.keyCode == 13) will cause the postback to the server. I know I can link this event to the button_click, but have to cancel the event like:

if (window.event.keyCode == 13) {
           event.returnValue=false;
           event.cancel = true;
           updateButton.click();
}

Otherwise the page will be submitted twice (right?).

My question is how the 'Enter key pressed' causes the postback? I wrote a simple page to test, it didn't mean like whenever there's page, pressing the enter key would cause the form to submit. Also, I didn't see other event_handler was called in Page_Load upon pressing the enter key. So seems to me that the submit wasn't thru a default button clicking. It must be wired into some JavaScript functions created by .NET on the backend without my permission. If so, can I disable it?

What if there are more than one form, which one to submit then?

Is there a way to catch this event, or to distinguish this event from a real button_click event on the Page_Load() function? So instead of doing but.click() on client side, I can explicitly call the handler on the server-side?

Thanks a lot.

D.
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Justin_W

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jnhorst

D:

When you create a FORM tag and put text boxes and a submit button, the browser will usually treat the Enter key as a command to submit the form.  It is as if you are calling the submit() method of the form object in JavaScript.

Depending on what controls you have on your page, ASP.NET might write a JavaScript function called __doPostBack() into your page.  The controls that do that use it to send information about the control and the postback to the server by putting that data in the __EVENTTARGET and __EVENTARGUMENT hidden text box fields that are also added to the HTML.  Then __doPostBack calls the submit() method of the form object.  So no, you are not necessarily posting the page back twice by hitting the enter key.  I can see some situations where you would not want the enter key to cause a postback and you can cacnel the event as you show in your question, but unless there is a reason to do so, it should not be necessary.

John
Avatar of ds869

ASKER

Thaks all.

I realized that I also have a couple of ImageButton controls on the page in the form of <input type='image'>. When I removed them from the form along with <input type=submit>, pressing the 'Enter' key won't trigger the form.submit().

Is there a way to set the imagebutton as 'input' intead of 'submit', e.g. using <input type='button'> instead of <input type='submit'> ? And although the imagebutton did trigger the form.submit, its event handler at the server-side wasn't called. Why?

The reason that pressing the Enter key submits the form twice is that I linked this event to a inputbutton.click which will submit the form, and it also triggers one of the imagebutton to submit the form, again. Those image button is for sorting the table only, which will be done at the server-side.

No one seems interested in answering my last question:

>Is there a way to catch this event, or to distinguish this event from a real button_click event on the Page_Load() function? So instead of >doing but.click() on client side, I can explicitly call the handler on the server-side?


Thanks again.

d.

Avatar of ds869

ASKER

So, if there's a submit button or an image button, the form will be submitted by enter.key.pressed, BUT not thru either one of the buttons, and the button's event handler at the server side won't be called. Is this right?
Avatar of ds869

ASKER

If I add the onClick to image button, like

<input type="image" name="te" id="te" src="./images/up.gif"  onClick="alert(event.keyCode)">

the event.keyCode is always 0, no matter I clicked on the image button or anywhere on the form.

Can anybody tell me why?

D.
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>Is there a way to catch this event,
I answered this above.

>or to distinguish this event from a real button_click event on the Page_Load() function?
No, not without catching the event on the client side.