ASP.net Gridview没有显示出来

Question

我有一个asp页面，我在彼此旁边显示两个gridview。第一个显示良好，但我看不到第二个。当我只显示一个identic版本时，会显示两个gridview。 您可以在下面找到我的页面的aspx代码。 数据源的查询在SQL中返回一条记录，因此有数据。更改查询时，EmptyDataText也不会显示。

 <asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
<table style="width:100%" class="table">
    <tr>
        <td style="width:50%; background-color: #2B71A5; border-style:solid; border-width:thin; border-color: Black">
            <asp:Label class="LabelHeader" ID="Label1" runat="server" Text="Filter:"  ></asp:Label>
            <asp:TextBox ID="txtFilter" Width="30%" runat= "server" OnTextChanged="txtFilter_TextChanged" AutoPostBack="true" />                                
            <asp:Button ID="cmdWisFilter" runat="server" Text="Wis" Width="10%" OnClick="cmdWis_Click" />
        </td>
        <td style="width:50%; background-color: #2B71A5; border-style:solid; border-width:thin; border-color: Black">
             <asp:DropDownList ID="ddlGebruikers" runat="server" DataSourceID="SqlDataSourceUser"
                 DataTextField="Naam" DataValueField="Naam" AutoPostBack="true"
                 OnSelectedIndexChanged="ddlGebruikers_SelectedIndexChanged" />
            <asp:SqlDataSource ID="SqlDataSourceUser" runat="server" 
                ConnectionString="<%$ ConnectionStrings:SqlConnectionStringNoProvider %>" 
                SelectCommand="SELECT Naam FROM tblGebruikers">
            </asp:SqlDataSource>
        </td>
    </tr>
</table>
<table style="width:100%" class="table">
    <tr>
        <td style="width:50%">
            <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
                DataKeyNames="ID" DataSourceID="SqlDataSource1" RowStyle-CssClass="RowStyle"
                EmptyDataText="There are no data records to display." AllowPaging="True" 
                AllowSorting="True" Width="100%" onsorted="GridView1_Sorted" 
                PageSize="15" HorizontalAlign="Left" CssClass="Grid" >
                <Columns>
                    <asp:TemplateField HeaderText="+">
                        <ItemTemplate>
                            <asp:ImageButton ID="cmdAdd" runat="server" ImageUrl="~/Images/add.ico" />
                        </ItemTemplate>
                    </asp:TemplateField>
                    <asp:TemplateField Visible="false">
                        <ItemTemplate>
                            <asp:Label ID="ID_Adres" runat="server" Text='<%# Bind("ID") %>' />
                        </ItemTemplate>
                    </asp:TemplateField>
                    <asp:BoundField DataField="Organisatie" HeaderText="Organisatie" ReadOnly="True" SortExpression="Organisatie" />
                    <asp:BoundField DataField="Adres" HeaderText="Adres" SortExpression="Adres" />
                    <asp:BoundField DataField="LaatstBezocht" HeaderText="Laatst bezocht" SortExpression="LaatstBezocht" />
                </Columns>
                    <HeaderStyle HorizontalAlign="Left" />
                    <PagerStyle CssClass="PagerStyle" />
            </asp:GridView>
            <asp:SqlDataSource ID="SqlDataSource1" runat="server"
                ConnectionString="<%$ ConnectionStrings:SqlConnectionStringNoProvider %>" 
                SelectCommand="SELECT ID, Organisatie, Dienst, Adres, Postcode, Stad, Contact, Telefoon, LaatstBezocht, Bezoekfrequentie From tblInstallatieadressen order by LaatstBezocht" 
                DeleteCommand="DELETE FROM tblInstallatieadressen WHERE ID=@ID"
                UpdateCommand="UPDATE tblInstallatieadressen SET Dienst=@Dienst, Adres=@Adres, Postcode=@Postcode, Stad=@Stad, Contact=@Contact, Telefoon=@Telefoon, LaatstBezocht=@LaatstBezocht, 
                    Bezoekfrequentie=@Bezoekfrequentie WHERE ID=@ID" >
                <DeleteParameters>
                    <asp:Parameter Name="ID" />
                </DeleteParameters>
                <UpdateParameters>
                    <asp:Parameter Name="Dienst" />
                    <asp:Parameter Name="Adres" />
                    <asp:Parameter Name="Postcode" />
                    <asp:Parameter Name="Stad" />
                    <asp:Parameter Name="Contact" />
                    <asp:Parameter Name="Telefoon" />
                    <asp:Parameter Name="LaatstBezocht" Type="DateTime" />
                    <asp:Parameter Name="Bezoekfrequentie" />
                </UpdateParameters>
            </asp:SqlDataSource>
        </td>
        <td style="width:50%">
            <asp:GridView ID="GridViewPlanningGebruiker" runat="server" AutoGenerateColumns="False" 
                DataSourceID="SqlDataSourcePlanning" RowStyle-CssClass="RowStyle"
                EmptyDataText="There are no data records to display." AllowPaging="True" onsorted="GridView1_Sorted" 
                AllowSorting="True" Width="100%" PageSize="15" HorizontalAlign="Left" CssClass="Grid" >
                <Columns>
                    <asp:BoundField DataField="ID_Installatieadres" HeaderText="Datum gepland" SortExpression="ID_Installatieadres" />
                </Columns>
                    <HeaderStyle HorizontalAlign="Left" />
                    <PagerStyle CssClass="PagerStyle" />
            </asp:GridView>
            <asp:SqlDataSource ID="SqlDataSourcePlanning" runat="server"
                ConnectionString="<%$ ConnectionStrings:SqlConnectionStringNoProvider %>" 
                SelectCommand="SELECT ID_Installatieadres, Gebruiker, DatumGepland from tblPlanning" >
            </asp:SqlDataSource>
        </td>
    </tr>
</table>

这是页面内容，包含2个网格视图。