AJAX PopupModalExtender
$<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<div class="pagetitle">Tasks</div>
<asp:UpdatePanel runat="server" ID="upTasks" UpdateMode="Conditional">
    <ContentTemplate>
        <asp:DropDownList runat="server" ID="drdFilter" AutoPostBack="true" OnSelectedIndexChanged="drdFilter_SelectedIndexChanged">
            <asp:ListItem Text="New" Value="1"/>
            <asp:ListItem Text="Completed" Value="2"/>
        </asp:DropDownList>
        <br /><br />
        <asp:GridView runat="server" ID="gvTasks" AutoGenerateColumns="False" DataKeyNames="ID" onselectedindexchanged="gvTasks_SelectedIndexChanged" CssClass="listTbl" BorderStyle="None">
           <Columns>
                <asp:BoundField DataField="ID" SortExpression="ID" HeaderText="Number" />
                <asp:BoundField DataField="CreatedDt" SortExpression="CreatedDt" HeaderText="Created" />
                <asp:BoundField DataField="TaskType" SortExpression="TaskType" HeaderText="Task Type" />
                <asp:BoundField DataField="TaskStatus" SortExpression="TaskStatus" HeaderText="Status" />
                <asp:BoundField DataField="Description" SortExpression="Description" HeaderText="Description" />
                <asp:BoundField DataField="ProductLineId" SortExpression="ProductLineId" HeaderText="ProductLineId" />
                <asp:CommandField ShowSelectButton="true" ControlStyle-Width="50" />
           </Columns>
        </asp:GridView>
    </ContentTemplate>
</asp:UpdatePanel>
<asp:Panel runat="server" ID="panViewTask" CssClass="popupDlg roundborder">
    <asp:UpdatePanel runat="server" ID="upViewTask" UpdateMode="Conditional">
        <ContentTemplate>
            <asp:ModalPopupExtender ID="panViewTask_ModalPopupExtender" runat="server"
                    DynamicServicePath="" Enabled="True" BackgroundCssClass="popupBg" CancelControlID="lbViewTaskCancel"
                    PopupControlID="panViewTask" TargetControlID="hlViewDetailsHidden" DropShadow="true" />
                <asp:HyperLink runat="server" ID="hlViewDetailsHidden" Text="Test" CssClass="invisible"></asp:HyperLink>
            <table class="formTbl width100">
                <tr>
                    <td colspan="2" class="error"><asp:Label runat="server" ID="lblError" /></td>
                </tr>
                <tr>
                    <th>ID</th>
                    <td><asp:Label runat="server" ID="lblTaskId"></asp:Label></td>
                </tr>
                <tr>
                    <th>Created Date</th>
                    <td><asp:Label runat="server" ID="lbCreatedDate"/></td>
                </tr>
                <tr>
                    <th>Task Type</th>
                    <td><asp:Label runat="server" ID="lbTaskType"></asp:Label><asp:LinkButton CssClass="padding" runat="server" ID="lbChangeCCInfo" Text="Change" onClick="lbChangeCCInfo_Click"></asp:LinkButton></td>
                </tr>
                <tr>
                    <th>Task Status</th>
                    <td><asp:Label runat="server" ID="lbTaskStatus"></asp:Label></td>
                </tr>
                <tr>
                    <th>Product Line ID</th>
                    <td><asp:Label runat="server" ID="lbProductLineId"></asp:Label></td>
                </tr>
                <tr>
                    <th>Customer Name</th>
                    <td><asp:Label runat="server" ID="lbName"></asp:Label></td>
                </tr>
                <tr>
                    <th>Phone Number</th>
                    <td><asp:Label runat="server" ID="lbPhoneNumber"></asp:Label></td>
                </tr>
                <tr>
                    <th>Rate Plan</th>
                    <td><asp:Label runat="server" ID="lbRatePlan"></asp:Label></td>
                </tr>
                <tr>
                    <th>Account Balance</th>
                    <td><asp:Label runat="server" ID="lbAccBalance"></asp:Label></td>
                </tr>
                <tr>
                    <th>Description</th>
                    <td><asp:Label runat="server" ID="lbDescription"></asp:Label></td>
                </tr>
                <tr id="trCompleted" runat="server">
                    <th>Completed</th>
                    <td><asp:CheckBox runat="server" ID="chkCompleted"></asp:CheckBox></td>
                </tr>
                <tr id="trCompletedDate" runat="server">
                    <th>Completed Date</th>
                    <td><asp:Label runat="server" ID="lbCompletedDate"></asp:Label></td>
                </tr>
                <tr>
                    <td colspan="2" class="buttonRow">
                        <asp:LinkButton runat="server" ID="lbViewTaskSave" Text="Save"
                            onclick="lbViewTaskSave_Click"></asp:LinkButton>
                        <asp:LinkButton runat="server" ID="lbViewTaskCancel" Text="Cancel"
                            onclick="lbViewTaskCancel_Click"></asp:LinkButton>
                    </td>
                </tr>
            </table>
            <asp:Panel runat="server" ID="panChangeCCInfo" CssClass="popupDlg roundborder">
                <asp:ModalPopupExtender ID="panChangeCCInfo_ModalPopupExtender" runat="server"
                    DynamicServicePath="" Enabled="True" BackgroundCssClass="popupBg" CancelControlID="lbCCInfoCancel"
                    PopupControlID="panChangeCCInfo" TargetControlID="lbChangeCCInfo" DropShadow="true" />
                <table class="formTbl">
                    <tr>
                        <th class="formHeader" style="font-weight:bold">
                            Add New Credit Card Information
                        </th>
                    </tr>
                    <tr>
                        <td>
                            <asp:Label runat="server" ID="lblCCNumber" />
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <uc1:CreditCardInput ID="ccInput" runat="server" />
                        </td>
                    </tr>
                    <tr>
                        <td class="buttonRow">
                            <asp:UpdateProgress runat="server" ID="UpdateProgress1">
                                <ProgressTemplate>
                                    <img src="../Images/progress.gif" / alt="">
                                </ProgressTemplate>
                            </asp:UpdateProgress>

                            <asp:LinkButton runat="server" ID="lbCCInfoSave" Text="Save"
                                onclick="lbCCInfoSave_Click"></asp:LinkButton>
                            <asp:LinkButton runat="server" ID="lbCCInfoCancel" Text="Cancel"
                                onclick="lbCCInfoCancel_Click"></asp:LinkButton>
                        </td>
                    </tr>
                </table>
            </asp:Panel>
        </ContentTemplate>
    </asp:UpdatePanel>
</asp:Panel>