<telerik:RadGrid ID="RadGrid1" runat="server" AllowPaging="True" Width="100%" PageSize="3"
            OnItemCommand="RadGrid1_ItemCommand"
            OnDetailTableDataBind="RadGrid1_DetailTableDataBind"
            OnNeedDataSource="RadGrid1_NeedDataSource">
            <MasterTableView Name="MasterTable" AutoGenerateColumns="true" DataKeyNames="OrderID">
                <DetailTables>
                    <telerik:GridTableView Name="ChildTable" DataKeyNames="OrderID" AutoGenerateColumns="true" CommandItemDisplay="Top">
                        <CommandItemTemplate>
                            <asp:LinkButton ID="btnEditSelected" runat="server" CommandName="EditSelected" CssClass="btn btn-default">Edit Selected</asp:LinkButton>
                        </CommandItemTemplate>
                    </telerik:GridTableView>
                </DetailTables>
            </MasterTableView>
            <ClientSettings>
                <Selecting AllowRowSelect="true" />
            </ClientSettings>
        </telerik:RadGrid>

    protected void RadGrid1_ItemCommand(object sender, GridCommandEventArgs e)
    {
        // Logic applies for all the tables (detail tables) which are not named "MasterTable"
        if(e.Item.OwnerTableView.Name != "MasterTable" && e.CommandName == RadGrid.EditSelectedCommandName)
        {
            e.Canceled = true;

            GridTableView detailTable = e.Item.OwnerTableView;

            if (detailTable.OwnerGrid.SelectedIndexes.Count == 0)
            {
                return;
            }

            foreach (GridDataItem selectedItem in detailTable.OwnerGrid.SelectedItems)
            {
                selectedItem.Edit = true;
            }

            detailTable.Rebind();
        }
    }

Protected Sub RadGrid1_ItemCommand(ByVal sender As Object, ByVal e As GridCommandEventArgs)
    If e.Item.OwnerTableView.Name <> "MasterTable" AndAlso e.CommandName = RadGrid.EditSelectedCommandName Then
        e.Canceled = True
        Dim detailTable As GridTableView = e.Item.OwnerTableView

        If detailTable.OwnerGrid.SelectedIndexes.Count = 0 Then
            Return
        End If

        For Each selectedItem As GridDataItem In detailTable.OwnerGrid.SelectedItems
            selectedItem.Edit = True
        Next

        detailTable.Rebind()
    End If
End Sub