1、前台代码：创建一个asp:TextBox控件和一个asp:Button按钮，隐藏掉按钮；

2、后台代码：绑定TextBox回车事件；

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">

    <script type="text/javascript">
        function EnterTextBox(button) {
            if (event.keyCode == 13) {
                event.keyCode = 9;
                event.returnValue = false;
                document.all[button].click();
            }
        }
    </script>
    <style>
        .btnClass {
            display: none;
        }
    </style>

    <asp:TextBox runat="server" ID="txt_value"></asp:TextBox>
    <asp:Button runat="server" ID="btn_btn" CssClass="btnClass" OnClick="btn_btn_Click" />
</asp:Content>

 public partial class _Default : Page
 {
     protected void Page_Load(object sender, EventArgs e)
     {
         txt_value.Attributes.Add("onkeypress", "btn_btn");
     }

     protected void btn_btn_Click(object sender, EventArgs e)
     {

     }
 }