Thank for your suggest，but it not work for me!
Here are my code, it always show some object is null and can not reference some object
can someone help me ?
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Default" %>
<head runat="server">
<title></title>
</head>
<body>
<input type="button" onclick="toggleGroups(null);" value="Toggle All" />
<input type="button" onclick="toggleGroups(0);" value="Toggle 1st" />
<input type="button" onclick="toggleGroups(1);" value="Toggle 2st" />
<form id="form1" runat="server">
<script type="text/javascript">
function toggleGroups(index) {
var gridClientID = '<%= RadGrid1.ClientID %>';
var grid = $find(gridClientID);
var masterTable = grid.get_masterTableView();
var groupToggles = masterTable._element.getElementsByTagName('INPUT');
if (index != null) {
if (index < groupToggles.length)
masterTable._toggleGroupsExpand(masterTable._element.getElementsByTagName('INPUT')[index], event);
}
else {
for (var i = 0; i < groupToggles.length; i++) {
masterTable._toggleGroupsExpand(masterTable._element.getElementsByTagName('INPUT')[i], event);
}
}
}
</script>
<div>
<telerik:RadScriptManager ID="RadScriptManager2" runat="server"></telerik:RadScriptManager>
<telerik:RadGrid ID="RadGrid1" runat="server" CellSpacing="0" DataSourceID="SqlDataSource1" AutoGenerateColumns="False" PageSize="5" AllowSorting="True" AllowPaging="True"
GridLines="None">
<PagerStyle Mode="NumericPages"></PagerStyle>
<MasterTableView GroupLoadMode="Client" DataKeyNames="CustomerID" DataSourceID="SqlDataSource1" HierarchyLoadMode="Client" >
<DetailTables>
<telerik:GridTableView DataKeyNames="OrderID" DataSourceID="SqlDataSource2" Width="100%"
runat="server" HierarchyLoadMode="Client">
<ParentTableRelation>
<telerik:GridRelationFields DetailKeyField="CustomerID" MasterKeyField="CustomerID" />
</ParentTableRelation>
<Columns>
<telerik:GridBoundColumn SortExpression="OrderID" HeaderText="OrderID" HeaderButtonType="TextButton"
DataField="OrderID" UniqueName="OrderID">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn SortExpression="OrderDate" HeaderText="Date Ordered" HeaderButtonType="TextButton"
DataField="OrderDate" UniqueName="OrderDate">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn SortExpression="EmployeeID" HeaderText="EmployeeID" HeaderButtonType="TextButton"
DataField="EmployeeID" UniqueName="EmployeeID">
</telerik:GridBoundColumn>
</Columns>
</telerik:GridTableView>
</DetailTables>
<Columns>
<telerik:GridBoundColumn DataField="CustomerID" FilterControlAltText="Filter CustomerID column" HeaderText="CustomerID" ReadOnly="True" SortExpression="CustomerID" UniqueName="CustomerID">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="CompanyName" FilterControlAltText="Filter CompanyName column" HeaderText="CompanyName" SortExpression="CompanyName" UniqueName="CompanyName">
</telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="ContactName" FilterControlAltText="Filter ContactName column" HeaderText="ContactName" SortExpression="ContactName" UniqueName="ContactName">
</telerik:GridBoundColumn>
</Columns>
</MasterTableView>
<ClientSettings AllowExpandCollapse="true">
</ClientSettings>
</telerik:RadGrid>
<br />
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>" SelectCommand="SELECT * FROM [Customers]"></asp:SqlDataSource>
<asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>" SelectCommand="SELECT * FROM [Orders] WHERE ([CustomerID] = @CustomerID)">
<SelectParameters>
<asp:SessionParameter Name="CustomerID" SessionField="CustomerID" Type="String" />
</SelectParameters>
</asp:SqlDataSource>
</div>
</form>
</body>
</html>