error comes when i try to bind gridview.
System.InvalidOperationException: 'Only one instance of a ScriptManager can be added to the page.'
 
Private Sub BindGrid()
    Dim cmd As New SqlCommand("SELECT Name,class as Classr,class,stream, House, ACNOS,admno,Sex,STDTYPE,Autofield FROM STUDENT")
    Stockbooks.DataSource = Me.ExecuteQuery(cmd, "SELECT")
    Stockbooks.DataBind()
    Stockbooks.UseAccessibleHeader = True
    Stockbooks.HeaderRow.TableSection = TableRowSection.TableHeader
End Sub
 
<body>
    <form id="form1" runat="server">
    <div class="auto-style1">
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script type="text/javascript" src="https://cdn.datatables.net/1.10.20/js/jquery.dataTables.min.js"></script>
    <link href="https://cdn.datatables.net/1.10.20/css/jquery.dataTables.css" rel="stylesheet" type="text/css" />
                <script type="text/javascript">
                    $(function () {
                        $("[id*=Stockbooks]").DataTable(
                            {
                                bLengthChange: true,
                                lengthMenu: [[15, 20, -1], [15, 20, "All"]],
                                bFilter: true,
                                bSort: true,
                                bPaginate: true
                            });
                    });
                </script>
    <div>
    <asp:GridView ID="Stockbooks" runat="server" AutoGenerateColumns="False" OnRowDataBound="OnRowDataBound" CssClass="w3-table-all w3-hoverable"
        HeaderStyle-BackColor="#FFCCCC" Width="50%" ClientIDMode="Static" Height="10px" ShowFooter = "True">
        <Columns>
            <asp:TemplateField>
                <HeaderTemplate>
                    <asp:CheckBox ID="chkAll" runat="server" AutoPostBack="true" OnCheckedChanged="OnCheckedChanged"/>
                </HeaderTemplate>
                <ItemTemplate>
                    <asp:CheckBox ID="CheckBox" runat="server" />
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField Visible="False">
                <ItemTemplate>
                    <asp:Label ID="admno" runat="server" Text='<%#Eval("admno")%>'> 
                     </asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"
                HeaderText="Admno">
                <FooterTemplate>
                    <asp:Button ID="Button1" runat="server" Text="AddNew Student" />
                </FooterTemplate>
                <ItemTemplate>
                    <asp:Label ID="Name" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px"
                        Text='<%#Eval("admno")%>'>
                    </asp:Label>
                </ItemTemplate>
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="white" />
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"
                HeaderText="Student Names">
                <FooterTemplate>
                    <asp:TextBox ID="Fnames" runat="server" Width="221px"></asp:TextBox>
                </FooterTemplate>
                <ItemTemplate>
                    <asp:Label ID="Class" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px"
                        Text='<%#Eval("Name") %>'>
                    </asp:Label>
                </ItemTemplate>
                <ControlStyle Width="250px" />
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="white" />
                <ItemStyle Width="50px" />
            </asp:TemplateField>
               <asp:TemplateField HeaderText = "Class">
                   <FooterTemplate>
                       <asp:DropDownList ID="ddlclasses" runat="server">
                           <asp:ListItem>ALL</asp:ListItem>
                           <asp:ListItem>PRE</asp:ListItem>
                           <asp:ListItem>P1</asp:ListItem>
                           <asp:ListItem>P2</asp:ListItem>
                           <asp:ListItem>P3</asp:ListItem>
                           <asp:ListItem>P4</asp:ListItem>
                           <asp:ListItem>P5</asp:ListItem>
                           <asp:ListItem>P6</asp:ListItem>
                           <asp:ListItem>P7</asp:ListItem>
                           <asp:ListItem>S1</asp:ListItem>
                           <asp:ListItem>S2</asp:ListItem>
                           <asp:ListItem>S3</asp:ListItem>
                           <asp:ListItem>S4</asp:ListItem>
                           <asp:ListItem>S5</asp:ListItem>
                           <asp:ListItem>S6</asp:ListItem>
                       </asp:DropDownList>
                   </FooterTemplate>
            <ItemTemplate>
                <asp:Label ID="lblCountry" runat="server" Text='<%# Eval("Class") %>' Visible = "False" />
                <asp:DropDownList ID="ddlclasses" runat="server">
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField >
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black" HeaderText="Stream">
                <FooterTemplate>
                    <asp:DropDownList ID="ddlstream" runat="server" DataSourceID="SqlDataSource1" DataTextField="Stream" DataValueField="Stream">
                    </asp:DropDownList>
                    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:STOREConnectionString1 %>" SelectCommand="SELECT [Stream] FROM [Streams]"></asp:SqlDataSource>
                </FooterTemplate>
               <ItemTemplate>
                    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                        <ContentTemplate>
                            <asp:DropDownList ID="ddlstream" runat="server">
                            </asp:DropDownList>
                            <asp:Label ID="Lblstream" runat="server" Text='<%# Eval("Stream") %>' Visible="False"></asp:Label>
                            <asp:ScriptManager ID="ScriptManager" runat="server" EnablePartialRendering="False">
                            </asp:ScriptManager>
                        </ContentTemplate>
                        <Triggers>
                            <asp:AsyncPostBackTrigger ControlID="ddlstream" EventName="SelectedIndexChanged" />
                        </Triggers>
                    </asp:UpdatePanel>
                </ItemTemplate>               
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="white" />
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"   HeaderText="Sex">
                <FooterTemplate>
                    <asp:DropDownList ID="ddlsex" runat="server">
                        <asp:ListItem>MALE</asp:ListItem>
                        <asp:ListItem>FEMALE</asp:ListItem>
                    </asp:DropDownList>
                </FooterTemplate>
                <ItemTemplate>
                    <asp:Label ID="lblsex" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px" />
                 <asp:Label ID="Lblsexd" runat="server" Text='<%# Eval("Sex").ToString() %>' Visible="False"></asp:Label>
                   
                    <asp:DropDownList ID="ddlsex" runat="server">
                    </asp:DropDownList>
                </ItemTemplate>
                <ControlStyle Width="100px"></ControlStyle>
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="Black" />
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"
                HeaderText="STDTYPE">
                <FooterTemplate>
                    <asp:DropDownList ID="ddlstdtype" runat="server">
                        <asp:ListItem>ALL</asp:ListItem>
                        <asp:ListItem>New</asp:ListItem>
                        <asp:ListItem>Old</asp:ListItem>
                        <asp:ListItem>OldRepeater</asp:ListItem>
                    </asp:DropDownList>
                </FooterTemplate>
                <ItemTemplate>
                    <asp:Label ID="lblstdtype" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px" Text='<%# Eval("STDTYPE") %>' Visible="False"></asp:Label>
                    <asp:DropDownList ID="ddlstdtype" runat="server">
                    </asp:DropDownList>
                </ItemTemplate>
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="Black"></HeaderStyle>
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"
                HeaderText="Colour">
                <FooterTemplate>
                    <asp:TextBox ID="Fcolour" runat="server"></asp:TextBox>
                </FooterTemplate>
                <ItemTemplate>
                    <asp:Label ID="Colour" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px"
                        Text='<%#Eval("House") %>'>
                    </asp:Label>
                </ItemTemplate>
                <ControlStyle Width="100px" />
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="Black"></HeaderStyle>
            </asp:TemplateField>
            <asp:TemplateField  HeaderStyle-Font-Names="Arial"  HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"  HeaderText="ACNOS"
                Visible="false">
                <ItemTemplate>
                    <asp:Label ID="ACNOS" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px"
                        Text='<%#Eval("ACNOS") %>'>
                    </asp:Label>
                </ItemTemplate>
                <ControlStyle Width="100px" />
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="white" />
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"
                Visible="false">
                <ItemTemplate>
                    <asp:Label ID="lblreminder" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px"
                        Text='<%#Eval("Classr") %>'>
                    </asp:Label>
                </ItemTemplate>
                <ControlStyle Width="100px" />
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="white" />
            </asp:TemplateField>
            <asp:TemplateField HeaderStyle-Font-Names="Arial" HeaderStyle-Font-Size="12px" HeaderStyle-ForeColor="Black"
                Visible="false">
                <ItemTemplate>
                    <asp:Label ID="lblpo" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="12px"
                        Text='<%#Eval("autofield") %>'>
                    </asp:Label>
                </ItemTemplate>
                <ControlStyle Width="100px" />
                <HeaderStyle Font-Names="Arial" Font-Size="12px" ForeColor="white" />
            </asp:TemplateField>
        </Columns>
        <EmptyDataTemplate>
            No Record Available
        </EmptyDataTemplate>
        <HeaderStyle BackColor="#4dc3ff" />
    </asp:GridView>
</div>
        </div>
    </form>
</body>
</html>