her is my aspx code
Code:
<div id="taskContainer">
<asp:UpdatePanel ID="updatetask" runat="server">
<ContentTemplate>
<asp:Panel ID="pnlTask" runat="server" Visible="false">
<table cellspacing="10">
<tr>
<td>
</td>
<td>
<input type="hidden" id="hidTask" runat="server" />
</td>
</tr>
<tr>
<td>
Task Subject</td>
<td class="mandatory">
<asp:TextBox ID="txtSubject" runat="server"></asp:TextBox> *</td>
</tr>
<tr>
<td>
Task Description</td>
<td class="mandatory">
<asp:TextBox ID="txtTask" runat="server"></asp:TextBox> *</td>
</tr>
<tr>
<td align="left">
Due Date</td>
<td class="mandatory">
<asp:TextBox ID="txtDate" runat="server" MaxLength="10" EnableTheming="false" CssClass="DateTextBox"></asp:TextBox> * <img
alt="Date Picker" src="Images/datePiker.jpg" style="cursor: hand; vertical-align: middle;"
onclick="CalendarPicker('<%=txtDate.ClientID%>')" />
</td>
</tr>
<tr>
<td>
Completed</td>
<td>
<asp:DropDownList ID="ddlCompleted" runat="server">
<asp:ListItem Text="Not Completed" Value="0"></asp:ListItem>
<asp:ListItem Text="Completed" Value="1"></asp:ListItem>
</asp:DropDownList>
</td>
</tr>
<tr>
<td>
Priority</td>
<td>
<asp:DropDownList ID="ddlPriority" runat="server">
<asp:ListItem Text="High" Value="High"></asp:ListItem>
<asp:ListItem Text="Normal" Value="Normal"></asp:ListItem>
<asp:ListItem Text="Low" Value="Low"></asp:ListItem>
</asp:DropDownList>
</td>
</tr>
</table>
<table>
<tr>
<td>
<asp:Button ID="btnSave" runat="server" Text="Save" OnClick="btnSave_Click" OnClientClick="return Validate()" /> <asp:Button
ID="btnCancel" Text="Cancel" runat="server" OnClick="btnCancel_Click" />
</td>
</tr>
</table>
</asp:Panel>
<asp:Panel ID="pnlTaskList" runat="server">
<table>
<tr>
<td class="arial-24">
Task</td>
</tr>
<tr>
<td>
<asp:GridView ID="gvTask" runat="server" AllowPaging="True" AutoGenerateColumns="False"
OnPageIndexChanging="gvTask_PageIndexChanging" PageSize="10" DataKeyNames="TSK_ID"
OnRowCommand="gvTask_RowCommand">
<Columns>
<asp:TemplateField HeaderText="CheckAll">
<HeaderTemplate>
<asp:CheckBox ID="chkSelectAll" runat="server" AutoPostBack="true" OnCheckedChanged="chkSelectAll_CheckedChanged"/>
</HeaderTemplate>
<ItemTemplate>
<input type="checkbox" id='chkDelete' runat="server" value='<%#Eval("TSK_ID")%>' />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="TSK_Subject" HeaderText="Subject" HeaderStyle-CssClass="pad-left"
ItemStyle-CssClass="pad-left" />
<asp:BoundField DataField="TSK_DueDate" HeaderText="Due Date" DataFormatString="{0:MM/dd/yyyy}"
HtmlEncode="false" />
<asp:BoundField DataField="TSK_Completed_1" HeaderText="Status" />
<asp:TemplateField>
<ItemTemplate>
<asp:UpdatePanel ID="updGv" runat="server">
<ContentTemplate>
<asp:LinkButton ID="lnkEdit" runat="server" Text="Edit" CommandName="EditRec" CommandArgument='<%#Eval("TSK_ID")%>'>
</asp:LinkButton>
</ContentTemplate>
</asp:UpdatePanel>
</ItemTemplate>
</asp:TemplateField>
</Columns>
<EmptyDataTemplate>
<table width="100%">
<tr>
<td runat="server" id="tdNoReocrdFound" class="vardana-16" style="border: 1px solid #ccc;
height: 25px">
<asp:Label ID="lblEmpty" runat="server" Text="No Record Found"></asp:Label>
</td>
</tr>
</table>
</EmptyDataTemplate>
</asp:GridView>
</td>
</tr>
</table>
</asp:Panel>
</ContentTemplate>
</asp:UpdatePanel>
</div>
<ajaxToolkit:UpdatePanelAnimationExtender ID="upae" BehaviorID="animation" runat="server" TargetControlID="updatetask">
<Animations>
<OnUpdating>
<Sequence>
<Parallel duration="0">
<EnableAction AnimationTarget="pnlTaskList" Enabled="false" />
<EnableAction AnimationTarget="pnlTask" Enabled="false" />
</Parallel>
<Parallel duration=".25" Fps="30">
<FadeOut AnimationTarget="taskContainer" minimumOpacity=".2" />
</Parallel>
</Sequence>
</OnUpdating>
<OnUpdated>
<Sequence>
<Parallel duration=".25" Fps="30">
<FadeIn AnimationTarget="taskContainer" minimumOpacity=".2" />
</Parallel>
<Parallel duration="0">
<EnableAction AnimationTarget="pnlTaskList" Enabled="true" />
<EnableAction AnimationTarget="pnlTask" Enabled="true" />
</Parallel>
<ScriptAction Script="changeOpacityDiv('taskContainer');" />
</Sequence>
</OnUpdated>
</Animations>
</ajaxToolkit:UpdatePanelAnimationExtender>