c# - 我通过一个下拉列表检查列表 View 的值，但我还有空白

很抱歉输入我的代码，但我不知道如何。

我有一个由下拉列表填充的列表视图，并且根据选项的不同，它显示了一些数据，但是保留空白以供我不使用的信息使用

dropdownlist和listview都链接到两个sqldatasources
下拉列表：

        <div>
        <asp:DropDownList ID="DropDownList1" runat="server"
        DataSourceID="SqlDataSource1" DataTextField="DenominazioneTipo"
        DataValueField="IdTipo" AutoPostBack="true">
        </asp:DropDownList>
        </div>

列表显示：

 <asp:ListView ID="ListView1" runat="server" DataSourceID="SqlDataSource2"
     DataKeyNames="ID" InsertItemPosition="LastItem">
            <EmptyDataTemplate>
                <table runat="server" style="background-color: #FFFFFF;
               border-collapse: collapse; border-color:
               #999999; border-style: none; border-width: 1px;">
                    <tr>
                   <td>Non è stato restituito alcun dato.</td>
                    </tr>
                </table>
            </EmptyDataTemplate>
            <InsertItemTemplate>
                <tr style="">
                    <td>
                <asp:Button ID="InsertButton" runat="server"
      CommandName="Insert" Text="Inserisci" OnClick="InsertButton_Click"
       Width="140px" />
                    </td>
                </tr>
            </InsertItemTemplate>
            <ItemTemplate>
                <tr style="background-color: #FFFBD6; color: #333333;">
                    <td>
              <asp:Button ID="DeleteButton" runat="server"
              CommandName="Delete"
              Text="Elimina" OnClientClick="return confirm
              ('Confermi la cancellazione del record?');" />
              <asp:Button ID="EditButton" runat="server"
              CommandName="Edit" Text="Modifica" ID_Persona='<%#
              Eval("ID") %>' OnClick="EditButton_Click" />
                    </td>

                    <td>
                <asp:Label ID="NomeLabel" runat="server" Text='<%#
                 Eval("Nome") %>' />
                    </td>
                    <td>
                        <asp:Label ID="CognomeLabel" runat="server" Text='<%# Eval("Cognome") %>' />
                    </td>
                    <td>
                        <asp:Label ID="CodiceFiscaleLabel" runat="server" Text='<%# Eval("CodiceFiscale") %>' />
                    </td>
                    <td>
                        <asp:Label ID="EmailLabel" runat="server" Text='<%# Eval("Email") %>' />
                    </td>
                    <td>
                        <asp:Label ID="RagioneSocialeLabel" runat="server" Text='<%# Eval("RagioneSociale") %>' />
                    </td>
                    <td>
                        <asp:Label ID="PivaLabel" runat="server" Text='<%# Eval("Piva") %>' />
                    </td>
                </tr>
            </ItemTemplate>



                <LayoutTemplate>
                <table runat="server">
                    <tr runat="server">
                        <td runat="server">

   <table id="itemPlaceholderContainer" runat="server" border="1"
   style="background-color: #FFFFFF;
   border-collapse: collapse; border-color: #999999;
   border-style: none; border-width: 1px;
     <tr runat="server" style="background-color: #FFFBD6; color:#333333;">
                <th runat="server"></th>
                <th runat="server">Nome</th>
                <th runat="server">Cognome</th>
                <th runat="server">CodiceFiscale</th>
                <th runat="server">Email</th>
                <th runat="server">RagioneSociale</th>
                <th runat="server">Piva</th>
                </tr>
                <tr id="itemPlaceholder" runat="server">
                </tr>
                </table>
               </asp:ListView>
        <asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:dbConnection %>" SelectCommand="SELECT [Nome], [Cognome], [Email], [CodiceFiscale], [RagioneSociale], [Piva], [ID] FROM [Persona] WHERE ([Tipocliente] = @Tipocliente)" DeleteCommand="DELETE FROM [Persona] WHERE [ID] = @original_ID" InsertCommand="INSERT INTO [Persona] ([Nome], [Cognome], [Email], [CodiceFiscale], [RagioneSociale], [Piva]) VALUES (@Nome, @Cognome, @Email, @CodiceFiscale, @RagioneSociale, @Piva)" OldValuesParameterFormatString="original_{0}" UpdateCommand="UPDATE [Persona] SET [Nome] = @Nome, [Cognome] = @Cognome, [Email] = @Email, [CodiceFiscale] = @CodiceFiscale, [RagioneSociale] = @RagioneSociale, [Piva] = @Piva WHERE [ID] = @original_ID">
            <DeleteParameters>
                <asp:Parameter Name="original_ID" Type="Int32" />
            </DeleteParameters>
            <InsertParameters>
                <asp:Parameter Name="Nome" Type="String" />
                <asp:Parameter Name="Cognome" Type="String" />
                <asp:Parameter Name="Email" Type="String" />
                <asp:Parameter Name="CodiceFiscale" Type="String" />
                <asp:Parameter Name="RagioneSociale" Type="String" />
                <asp:Parameter Name="Piva" Type="String" />
            </InsertParameters>
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList1" Name="Tipocliente" PropertyName="SelectedValue" Type="Int32" DefaultValue="1" />
            </SelectParameters>
            <UpdateParameters>
                <asp:Parameter Name="Nome" Type="String" />
                <asp:Parameter Name="Cognome" Type="String" />
                <asp:Parameter Name="Email" Type="String" />
                <asp:Parameter Name="CodiceFiscale" Type="String" />
                <asp:Parameter Name="RagioneSociale" Type="String" />
                <asp:Parameter Name="Piva" Type="String" />
                <asp:Parameter Name="original_ID" Type="Int32" />
            </UpdateParameters>
        </asp:SqlDataSource>

预先感谢您的合作

最佳答案

**在注释中添加此示例代码时出错。所以我
  将其放入答案中。在文件后面的代码中添加代码，就像
  请找到合适的活动去做
  **

if(NomeLable.text !=null)
{
   NomeLable.visible = true ;
}
else
{
   NomeLable.visible = false;
 }