单击重置按钮时为什么会先触发验证控件啊 而不是直接清除内容重置啊 大侠帮我看看
前台代码：
<td align="right" class="style5">
                        用户名：</td>
                    <td align="left">
                        <asp:TextBox ID="tb_name" runat="server"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
                            ControlToValidate="tb_name" ErrorMessage="用户名不能为空！"></asp:RequiredFieldValidator>
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                        用户密码：</td>
                    <td align="left">
                        <asp:TextBox ID="tb_pwd" runat="server" TextMode="Password"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server"
                            ControlToValidate="tb_pwd" ErrorMessage="密码不能为空"></asp:RequiredFieldValidator>
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                        确认密码：</td>
                    <td align="left">
                        <asp:TextBox ID="tb_pwdsure" runat="server" TextMode="Password"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server"
                            ControlToValidate="tb_pwdsure" ErrorMessage="**"></asp:RequiredFieldValidator>
                        <asp:CompareValidator ID="CompareValidator1" runat="server"
                            ControlToCompare="tb_pwd" ControlToValidate="tb_pwdsure" ErrorMessage="密码不一致"></asp:CompareValidator>
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                        真实姓名： </td>
                    <td align="left">
                        <asp:TextBox ID="tb_tname" runat="server"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                         Email： </td>
                    <td align="left">
                        <asp:TextBox ID="tb_email" runat="server"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server"
                            ControlToValidate="tb_email" ErrorMessage="Email不能为空"></asp:RequiredFieldValidator>
                        <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
                            ControlToValidate="tb_email" ErrorMessage="*"
                            ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                        性别：</td>
                    <td align="left">
                        <asp:RadioButtonList ID="Rblsit" runat="server" RepeatDirection="Horizontal"
                            Width="92px">
                            <asp:ListItem Selected="True">男</asp:ListItem>
                            <asp:ListItem>女</asp:ListItem>
                        </asp:RadioButtonList>
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                        出生日期：</td>
                    <td align="left">
                        <asp:TextBox ID="tb_bth" runat="server"></asp:TextBox>
                  
                    </td>
                </tr>
                <tr>
                    <td align="right" class="style5">
                        电话号码：</td>
 <td align="center" class="style8">
            <asp:Button ID="tb_tjiao" runat="server" Text="提交" onclick="tb_tjiao_Click" />
            &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
            <asp:Button ID="tb_reset" runat="server" Text="重置" UseSubmitBehavior="False"
                onclick="tb_reset_Click" />
        </td>
后台代码：
protected void tb_reset_Click(object sender, EventArgs e)
    {
        if (Page.IsPostBack)
        {
            tb_email.Text = "";
            tb_name.Text = "";
            tb_pwd.Text = "";
            tb_bth.Text = "";
            tb_phone.Text = "";
            tb_pwdsure.Text = "";
            tb_tname.Text = "";
        }
    }