网页开发中最烦人的事情之一就是为表单处理"Enter key" ,"Enter key"已经成为用户提交表单的偏好。虽然我们为用户提供了提交按钮，但是最简单也是最直接的方式仍然是：输入文字，然后回车完成提交
ASP.NET 2.0中为此提供了很好的解决方法。只需要将"defaultbutton"属性指定到想要引发事件的按钮控件的ID上就可以了。
在表单级别和面板级别（<asp:panel> 标记）均可以指定"defaultbutton"。当表单和面板中同时指定了defaultbutton，则如果在面板中触发了"Enter key",则执行面板中的
下面的实例代码中有一个表单和4个面板，报单和面板中都有按钮。情各位注意：在文本框中回车后会触发哪些按钮的事件
<form id="form1" runat="server" defaultbutton="btn1">
<div>
<asp:TextBox ID="txt" runat="server"></asp:TextBox>
<asp:Button ID="Button5" runat="server" Text="Cancel" OnClick="Button5_Click" />
<asp:Button ID="btn1" runat="server" Text="Submit" OnClick="btn1_Click" />
<asp:Panel ID="pnl1" runat="server" defaultbutton="Button1">
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button1" OnClick="Button1_Click" />
</asp:Panel>
<asp:Panel ID="Panel1" runat="server" defaultbutton="Button2">
<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>
<asp:Button ID="Button2" runat="server" Text="Button2" OnClick="Button2_Click" />
</asp:Panel>
<asp:Panel ID="Panel2" runat="server" defaultbutton="Button3">
<asp:TextBox ID="TextBox5" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox6" runat="server"></asp:TextBox>
<asp:Button ID="Button3" runat="server" Text="Button3" OnClick="Button3_Click" />
</asp:Panel>
<asp:Panel ID="Panel3" runat="server" defaultbutton="Button4">
<asp:TextBox ID="TextBox7" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox8" runat="server"></asp:TextBox>
<asp:Button ID="Button4" runat="server" Text="Button4" OnClick="Button4_Click" />
</asp:Panel>
</div>
</form>
The corresponding, sample events for the button clicks are
protected void Button1_Click(object sender, EventArgs e)
{
Response.Write(Button1.Text);
}
protected void Button2_Click(object sender, EventArgs e)
{
Response.Writ
