<div id="divContent" runat="server" style="display: none;">
<asp:Table ID="MainContainer" style="width:99%; height:92%; margin-left:1%; margin-right:0%;" runat="server">
<asp:TableRow>
<asp:TableCell ColumnSpan="2">
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell id="tdTimelineCell" CssClass="TimelineCell" runat="server"></asp:TableCell>
<asp:TableCell id="tdSummaryCell" CssClass="SummaryCell" runat="server">
<div style="overflow: auto; width: 100%; height: 100%;">
<telerik:RadGrid ID="SummaryRadGrid" runat="server">
<MasterTableView AutoGenerateColumns = "false">
<Columns>
<telerik:GridBoundColumn DataField="Id" Visible="false"></telerik:GridBoundColumn>
<telerik:GridTemplateColumn HeaderStyle-CssClass="HeaderEpisodeMarginLeft"></telerik:GridTemplateColumn>
<telerik:GridBoundColumn DataField="Remote_Index" visible="false"></telerik:GridBoundColumn>
<telerik:GridBoundColumn DataField="Time_Effective" Visible="false"></telerik:GridBoundColumn>
<telerik:GridTemplateColumn HeaderStyle-CssClass="HeaderEpisodeMarginRight"></telerik:GridTemplateColumn>
</Columns>
</MasterTableView>
</telerik:RadGrid>
<asp:label id="lblNoRecords" runat="server" visible="false" CssClass="NoRecords">
<asp:Literal id="litNoRecords" runat="server" enableviewstate="false">No records</asp:Literal>
</asp:label>
</div>
</asp:TableCell>
</asp:TableRow>
</asp:Table>
</div>
var
grid = $("#MainContainer tdSummaryCell").find("SummaryRadGrid").get_masterTableView();
var dgrSummary = $find('<%=SummaryRadGrid.ClientID %>').get_masterTableView();
and many other ways but none of them worked.

<script type="text/javascript"> $(document).ready(function () { //expand details row to show more data on a certain work $(".rgExpandCol").live("mouseover", function (event) { var masterTable = $find("<%= Grid1.ClientID %>").get_masterTableView(); //collapse all for (var i = 0; i < masterTable.get_dataItems().length; i++) { masterTable.collapseItem(i); } //expend row for (var i = 0; i < masterTable.get_dataItems().length; i++) { if (masterTable.get_dataItems()[i].get_element() == $(this).parent()[0]) { masterTable.expandItem(i); break; } } }); });</script>