更新面板不是已知元素

>我在我的aspx文件中收到上述错误"更新面板不是已知元素....."使用 Visual Studio 2013

我认为我的 web.config 文件可能存在问题，它的外观是它的外观

<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
</configSections>
  <system.web>
    <compilation debug="true" targetFramework="4.5" />  
    <httpRuntime targetFramework="4.5" />
  <pages>
      <controls>
        <add tagPrefix="ajaxToolkit" assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" />
      </controls>
    </pages></system.web>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>

我认为这行可能是一个问题：

<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />

有谁知道如何处理这个问题？Ajax 工具包已从 NuGet 安装

ASPX 文件如下我在更新面板上收到错误，说它不是已知元素

 <asp:ScriptManager ID="ScriptManager1" runat="server">
            <asp:UpdatePanel ID="UpdatePanel1" runat="server">

            <div id="divContactDetails" class="cssDivContactDetails">
                <asp:GridView ID="GridView1" CssClass="cssGridView1" runat="server" DataSourceID="SqlDataSource1" AllowSorting="false" RowStyle-Wrap="true" AutoGenerateColumns="False" 
                    BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px" CellPadding="3" CellSpacing="2"
                    DataKeyNames="ContactID" Width="86%" EmptyDataText="There is donation data to be displayed" OnRowDataBound="GridView1_RowDataBound" OnRowEditing="GridView1_RowEditing" >
                    <Columns>
                        <asp:CommandField ShowSelectButton="True" />
                        <asp:BoundField DataField="ContactID" HeaderText="ContactID" SortExpression="ContactID" InsertVisible="False" ReadOnly="True" ></asp:BoundField>
                        <asp:BoundField DataField="Forename" HeaderText="Forename" SortExpression="Forename" ReadOnly="true"></asp:BoundField>
                        <asp:BoundField DataField="Surname" HeaderText="Surname" SortExpression="Surname" ReadOnly="true"></asp:BoundField>
                        <asp:BoundField DataField="AddressLine1" HeaderText="AddressLine1" SortExpression="AddressLine1" ReadOnly="true"></asp:BoundField>
                        <asp:BoundField DataField="AddressLine2" HeaderText="AddressLine2" SortExpression="AddressLine2" ReadOnly="true"></asp:BoundField>
                        <%--                 <asp:ButtonField Text="Quick Donate" ButtonType="Button" CommandName="InsertQuickDonation" CommandArgument="<%# ((GridViewRow) Container).RowIndex %>">
                 <ItemStyle CssClass="tableTextContactDetails" />
                 </asp:ButtonField>--%>
                        <asp:TemplateField HeaderText="Quick Donate">
                            <ItemTemplate>
                                <asp:Button ID="btnQuickDonate" runat="server"
                                    CommandName="Insert"
                                    CommandArgument="<%# ((GridViewRow) Container).RowIndex %>"
                                    OnClick="btnQuickDonate"
                                    Text="Quick Donate" />
                            </ItemTemplate>
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="No Donate">
                            <EditItemTemplate>
                                <asp:DropDownList ID="drpNoDonateReasons" runat="server">
                                    <asp:ListItem>Already Paid</asp:ListItem>
                                    <asp:ListItem>Direct Debit</asp:ListItem>
                                    <asp:ListItem>Colletion Missed</asp:ListItem>
                                    <asp:ListItem>Parent not at Home</asp:ListItem>
                                    <asp:ListItem>No Money</asp:ListItem>
                                </asp:DropDownList>
                              <asp:Button ID="BtnCancel" runat="server" 
                                  CommandName="Cancel" 
                                  Text="Cancel" 
                                  OnClick="BtnCancel_Click" />
                                <asp:Button ID="BtnInsert" runat="server" 
                                    CommandName="Insert"
                                    CommandArgument="<%# ((GridViewRow) Container).RowIndex %>" 
                                    Text="Insert" 
                                    OnClick="btnNoDonate" />
                            </EditItemTemplate>
                            <ItemTemplate>
                                <asp:Button ID="btnNoDonate" runat="server"
                                    CommandName="Edit"
                                    CommandArgument="<%# ((GridViewRow) Container).RowIndex %>"
                                    OnClick="btnNoDonation"
                                    Text="No Donate" />
                            </ItemTemplate>

                        </asp:TemplateField>

                    </Columns>
                    <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
                    <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
                    <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
                    <RowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
                    <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
                    <SortedAscendingCellStyle BackColor="#FFF1D4" />
                    <SortedAscendingHeaderStyle BackColor="#B95C30" />
                    <SortedDescendingCellStyle BackColor="#F1E5CE" />
                    <SortedDescendingHeaderStyle BackColor="#93451F" />
                </asp:GridView>
                </div>
                </asp:UpdatePanel>
                </asp:ScriptManager>

Grundy的建议给了我以下运行：

Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. 
Parser Error Message: Could not load file or assembly 'Microsoft.AspNet.Web.Optimization.WebForms' or one of its dependencies. The system cannot find the file specified.
Source Error: 

[No relevant source lines]
Source File: none    Line: 0 
Assembly Load Trace: The following information can be helpful to determine why the assembly 'Microsoft.AspNet.Web.Optimization.WebForms' could not be loaded.

=== Pre-bind state information ===
LOG: DisplayName = Microsoft.AspNet.Web.Optimization.WebForms
 (Partial)
WRN: Partial binding information was supplied for an assembly:
WRN: Assembly Name: Microsoft.AspNet.Web.Optimization.WebForms | Domain ID: 2
WRN: A partial bind occurs when only part of the assembly display name is provided.
WRN: This might result in the binder loading an incorrect assembly.
WRN: It is recommended to provide a fully specified textual identity for the assembly,
WRN: that consists of the simple name, version, culture, and public key token.

设法安装了Microsoft.AspNet.Web.Optimization.WebForms.dll它在Web表单中创建了一个条目，如下所示：

  <add assembly="Microsoft.AspNet.Web.Optimization.WebForms" namespace="Microsoft.AspNet.Web.Optimization.WebForms" tagPrefix="webopt" />

但仍然没有运气，更新面板仍然未知。
同样在做

using system.web.extensions

它

似乎没有找到 .extensions，我已经检查了参考，它肯定在那里！