验证无法正常工作

我有一个文本框，按下链接按钮时会启用该文本框。每次我删除文本框的内容并点击取消时，我都希望它不进行任何验证。它执行客户端验证，当我第二次点击取消时，页面会像它应该的那样返回。这是我的 HTML。我真的需要弄清楚这一点。谢谢。

<%@ Page Title="Account Activation Deactivation Reasoning" Language="C#" MasterPageFile="~/Forms/Site.master"
AutoEventWireup="True" CodeBehind="ActivationDeactivationReasons.aspx.cs" Inherits="AccountManagementAdmin.UserInterface.Forms.ActivateDeactivateReasons.ActivationDeactivationReasons" %>
<%@ MasterType VirtualPath="~/Forms/Site.Master" %>
<asp:Content ID="cphAccNumberLookup" runat="server" ContentPlaceHolderID="cphPageContent">
    <div class="ContentPage">
        <div class="ContentPageHeader">
            Activation/Deactivation Account Reasons
        </div>
            <asp:Panel runat="server" EnableViewState="false" ID="pnlMessage" Visible="false">
                    <asp:Label runat="server" ID="lblValidationMessage" EnableViewState="false" />
            </asp:Panel>
        <br />
        <div class="SubSection">
            <div class="SubSectionHeader">
                Add Activation/Deactivation Reason
            </div>
            <table>
                <tr>
                    <td>
                        <asp:Label ID="lblReason" runat="server" Text="Enter Reason:"></asp:Label>
                    </td>
                    <td>
                        <asp:TextBox ID="txtNewReason" runat="server" MaxLength="30" Width="206px"></asp:TextBox>
                    </td>
                    <td>
                        <asp:Button ID="btnAdd" runat="server" Text="Add" CssClass="Button" OnClick="btnAdd_Click">
                        </asp:Button>
                    </td>
                </tr>
            </table>
        </div>
        <br />
        <div>
            <table>
                <asp:Repeater runat="server" ID="rptReasons" 
                    onitemcommand="rptReasons_ItemCommand">
                    <HeaderTemplate>
                        <thead>
                            <tr>
                                <th class="GridHeader">
                                    Reason
                                </th>
                                <td class="GridHeader">
                                </td>
                            </tr>
                        </thead>
                    </HeaderTemplate>
                    <ItemTemplate>
                        <tr>
                            <td class="GridRow" style="text-align: left;">
                                <asp:Label runat="server" ID="lblValue" Text='<%# DataBinder.Eval(Container.DataItem, "Description") %>'/>
                                <asp:TextBox runat="server" ID="txtValue" ValidationGroup="validationGroup" Visible="false" Width="550" Text='<%# DataBinder.Eval(Container.DataItem, "Description") %>' />
                                <asp:RequiredFieldValidator ID="rfvReasons" runat="server" ValidationGroup="validationGroup" ControlToValidate="txtValue" Display="Dynamic"  ErrorMessage="Reason Cannot Be Empty"/>
                                <asp:RegularExpressionValidator runat="server" ID="regxValidator" ControlToValidate="txtValue" Display="Dynamic" ValidationExpression="^[A-Za-z0-9 *~!@#$%^&*()|''?/<>=+_]+$" ErrorMessage="Reason Contains Invalid Characters"/>
                                </td>
                            <td class="GridRow" style="width: 80px;">
                                <asp:LinkButton runat="server" ID="lbtnEdit" Text="Edit" CommandName="Edit"/>
                                <%--<asp:Panel runat="server" ID="pnlUpdateRow" Visible="false" >--%>
                                    <asp:Button runat="server" ID="lbtnUpdate" Text="Update" CommandName="Update"  CommandArgument= '<%# DataBinder.Eval(Container.DataItem, "Id") %>' Visible="False" ValidationGroup="validationGroup" CausesValidation="True"/>
                                    <asp:Button runat="server" ID="lbtnCancel" Text="Cancel" CommandName="Cancel" Visible="False/>
                                <%--</asp:Panel>--%>
                            </td>
                        </tr>
                    </ItemTemplate>
                </asp:Repeater>
            </table>
        </div>
    </div>
</asp:Content>