code snippet 1

ASPX

<html>
<head runat="server">
    <title></title>
    <script src="Script/jquery-1.10.2.min.js"></script>
    <telerik:RadCodeBlock ID="RadCodeBlock1" runat="server">
        <script>

            function OnRowSelected(sender, args) {
                var id = args.getDataKeyValue("ID");
                $find("<%= RadAjaxManager1.ClientID %>").ajaxRequest("SelectedMP," + id);
            }

        </script>
    </telerik:RadCodeBlock>
</head>
<body>
    <form id="form1" runat="server">
        <div>
            <telerik:RadScriptManager ID="RadScriptManager1" EnablePageMethods="true" runat="server">
            </telerik:RadScriptManager>
            <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server" OnAjaxRequest="RadAjaxManager1_AjaxRequest">
                <AjaxSettings>
                    <telerik:AjaxSetting AjaxControlID="RadAjaxManager1">
                        <UpdatedControls>
                            <telerik:AjaxUpdatedControl ControlID="RadGrid2" />
                        </UpdatedControls>
                    </telerik:AjaxSetting>
                </AjaxSettings>
            </telerik:RadAjaxManager>
            <telerik:RadGrid ID="RadGrid1" runat="server" AutoGenerateColumns="false" OnNeedDataSource="RadGrid1_NeedDataSource"
                AllowFilteringByColumn="true" AllowPaging="true" ShowGroupPanel="true" GroupingEnabled="true" PageSize="10">
                <PagerStyle AlwaysVisible="true" Mode="NextPrevAndNumeric" />
                <MasterTableView DataKeyNames="ID" ClientDataKeyNames="ID">
                    <Columns>
                        <telerik:GridBoundColumn DataField="ID" UniqueName="ID" HeaderText="ID">
                        </telerik:GridBoundColumn>
                        <telerik:GridBoundColumn DataField="Name" UniqueName="Name" HeaderText="Name">
                        </telerik:GridBoundColumn>
                        <telerik:GridEditCommandColumn></telerik:GridEditCommandColumn>
                    </Columns>
                </MasterTableView>
                <ClientSettings AllowDragToGroup="true" AllowKeyboardNavigation="true">
                    <ClientEvents OnRowSelected="OnRowSelected" />
                    <KeyboardNavigationSettings EnableKeyboardShortcuts="true" />
                    <Selecting AllowRowSelect="true" />
                </ClientSettings>
            </telerik:RadGrid>

            <telerik:RadGrid ID="RadGrid2" runat="server"></telerik:RadGrid>
        </div>
    </form>
</body>
</html>


ASPX.CS


    protected void RadGrid1_NeedDataSource(object sender, GridNeedDataSourceEventArgs e)
    {
        List<Employee> list = new List<Employee>(); ;

        Employee obj = new Employee();
        obj.ID = "1";
        obj.Name = "Name1";
        list.Add(obj);

        obj = new Employee();
        obj.ID = "2";
        obj.Name = "Name2";
        list.Add(obj);

        RadGrid1.DataSource = list;
    }

    protected void RadAjaxManager1_AjaxRequest(object sender, AjaxRequestEventArgs e)
    {
        string[] strArgs = e.Argument.Split(',');
        if (strArgs[0] == "SelectedMP")
        {
            string id = strArgs[1];

            List<Employee> list = new List<Employee>(); ;

            Employee obj = new Employee();
            obj.ID = id;
            obj.Name = "Name1";
            list.Add(obj);


            RadGrid2.DataSource = list;
            RadGrid2.DataBind();
        }
    }
.................
.................

[Serializable]
public class Employee
{
    public string ID { get; set; }
    public string Name { get; set; }
    public bool IsActive { get; set; }
}