ASP.NET: How to specify which button should defaultly react for an Enter press?

I have a webpage where there are two buttons and a textbox. When the page loads and user presses enter, the first button is clicked - and that is ok.

I would like to assure that if user enters the textBox and types anything there and THEN presses enter, the second button is clicked. When I enter the textBox I can tell that the first button will be used when I press enter, because it is a bit dark-blue-bordered then开发者_高级运维.

I tried javascript's

if (event && event.keyCode == 13)
    document.getElementById("Button2").click();

but it somehow doesn't work. So my second thought was that there must be a possibility to tell the browser which button should defaultly react for an enter press when I'm in a specific textBox (the dark-blue-bordered button).

Edit: it might matter that first button is input and the second one is asp:Button

Edit2: Page.Form.DefaultButton is not an option, as there are somehow two default buttons. One should be clicked if user doesn't enter a textBox, other one if he is inside the textBox. Changing DefaultButton is not an option as this would require a postback after entering textBox by a user...

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The Page.Form.DefaultButton allows to set which button will react to the Enter key.

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<asp:Panel runat="server" DefaultButton="Button2" >
    <asp:TextBox runat="server" />
    <asp:Button ID="Button2" runat="server" Text="Button2" OnClientClick="alert('Button2')"/>
</asp:Panel>

As soon as you start using the textbox - button2 will be the default button. Up until then the other button will be the default

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DefaultButton property