Enter Key in ASP.NET - Complete Research

One of the common requests in ASP.NET is to submit a form when visitor hit an Enter key. That could be a case if, for example you want to make Login Screen. It is expected that user just hit enter when he insert a password instead to of forcing him to use a mouse to click login button. If you want to make search function on your web site, it is frequently required to give a possiblity to hit enter after you insert a search terms instead of mouse click on a Search button.

In classic HTML or ASP pages, it is not hard to submit forms using the enter key. Programmer use a to make a default button. If web site visitor click on that button or press enter key, the form will be submited.

Off course, you can have a more than one form on your page and individual submit button for every form.

You don't want to submit a form with Enter key?
Rarely, you will need to disable an Enter key and avoid to submit form. If you want to prevent it completely, you need to use OnKeyDown handler on tag of your page. The javascript code should be:

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

ASP.NET problems with Enter key
If you try to use Enter key in ASP.NET, according to your browser's type, you can get really weird results. Try to place one ASP.NET textbox and a button to the web form. Write a code on a OnClick event of a button. That could be something simple, like:

  Response.Write("The button was clicked!");  

Now start debuging and write something to textbox. If you press enter while focus is on textbox, form will submit, but your code for button's click event will not be executed.

Stop the debuging and place one simple HTML textbox to the form. You will not write anything in this textbox, so you can make it invisible. Just place this HTML code somewhere inside of your form tag.

    

Start debuging again. You cannot see the second textbox, and everything looks like before. Try again to write something in visible textbox. If you press enter now, form will submit, and also your code for button's click event will be executed. This is extremelly different behavior, and you did nothing except you placed one inivisible HTML textbox on web form. :)

Maybe it is not elegant, but placing invisible textbox could be simple solution for you if you have only one button on your web form. But, what if you have a different situation? What if you have a few buttons with only one textbox, more than one text box with only one button, or many text boxes and many buttons on form?

Different browsers has a different behaviors in these cases. if you have more buttons, only first button will be "clicked" every time. So, we need some other approach to get an universal solution.

How to make a default button in ASP.NET
We need to specify exactly what button will be "cliked" when visitor press Enter key, according to what textbox currently has a focus. The solution could be to add onkeydown attribute to textbox control:

  TextBox1.Attributes.Add("onkeydown", "if(event.which || event.keyCode){if ((event.which == 13) || (event.keyCode == 13)) {document.getElementById('"+Button1.UniqueID+"').click();return false;}} else {return true}; ");  

This line of code will cause that button Button1 will be "clicked" when visitor press Enter key and cursor is placed in TextBox1 textbox. On this way you can "connect" as many text boxes and buttons as you want.

Easy solution for default button
There is a free component that allows you to assign a button to the "enter-pressed" client side event of input controls. If you type some text in textbox and press Enter, the form will postback, and the serverside click event of your button is fired.You don't need to write any code You only need to use control's "DefaultButton" property. It you are a beginner programmer this could be a life saver. More about MetaBuilders DefaultButtons Control you can find at http://www.metabuilders.com/Tools/DefaultButtons.aspx

Default buttons in ASP.NET 2.0
ASP.NET 2.0 makes this problems easier and introduce a concept of a "default button". New defaultbutton attribute can be used with

or control. What button will be "clicked" depends of where acutally cursor is and what button is choosen as a default button for form or a panel.

Here is sample HTML code that contains one form and one panel control:
<form defaultbutton=“button1”
                                  runat=“server”>

                                      <asp:textbox id=“textbox1”
                                  runat=“server”/>

                                      <asp:textbox id=“textbox2”
                                  runat=“server”/>

                                      <asp:button id=“button1”
                                  text=“Button1” runat=“server”/>

                                  

                                      <asp:panel defaultbutton=“button2”
                                  runat=“server”>

                                          <asp:textbox
                                  id=“textbox3” runat=“server”/>

                                          <asp:button
                                  id=“button2” runat=“server”/>

                                      </asp:panel>

                                  

                                  </form>

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