LinqDataSource - 过滤空值

发布于 2024-09-14 20:49:11 字数 2021 浏览 9 评论 0原文

我正在编写一个 ASP.Net Web 应用程序。我有 listview，它的数据源是 LinqDataSource。在我的数据库中，我有一个员工表，我正在尝试使用下拉列表过滤他们的团队的记录。这工作正常，直到我在下拉列表中选择“全部”。它返回除 teamID 为空的人员之外的所有人员。如何返回 teamID 为 null 的记录？

这是我的代码：

<asp:ListView ID="ListView1" runat="server" DataSourceID="ldsStaff" DataKeyNames="staffID">

    <LayoutTemplate>
<table>
  <tr>
     <th>Name</th>
     <th>Team</th>
  </tr>
  <tr>
     <td>&nbsp</td>
     <td><asp:DropDownList ID="ddlTeamFilter" runat="server" DataSourceID="ldsTeams" DataTextField="Team" DataValueField="TeamID" AppendDataBoundItems="true" AutoPostBack="true">
        <asp:ListItem Text="[All]" Value=""></asp:ListItem>
         </asp:DropDownList>
     </td>
  </tr>
  <tr ID="itemPlaceHolder" runat="server"></tr>
</table>
</LayoutTemplate>
....
</asp:Listview>

<asp:LinqDataSource ID="ldsStaff" runat="server" 
    ContextTypeName="ProjectDatabase.ProjectDatabaseUsersDataContext" OrderBy="name" 
    TableName="Staffs" EnableUpdate="True" Where="inService == @inService &amp;&amp; TeamID == @TeamID">
    <WhereParameters>
        <asp:Parameter DefaultValue="true" Name="inService" Type="Boolean" />
        <asp:ControlParameter ControlID="ctl00$ContentPlaceHolder1$ListView1$ddlTeamFilter" Name="TeamID" Type="Int32" PropertyName="SelectedValue"/>
     </WhereParameters>
</asp:LinqDataSource>

在我的代码后面，我处理 LinqDataSource 选择事件：

Private Sub ldsStaff_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles ldsStaff.Selecting
    Dim ddl As DropDownList = CType(ListView1.FindControlRecursive("ddlTeamFilter"), DropDownList)
    If ddl.SelectedValue = "" Then
        e.WhereParameters.Remove("TeamID")
    End If

我认为如果我在下拉列表为“全部”时删除 where 参数，它将强制它返回所有记录，但它不起作用。

请帮忙！

谢谢，艾玛

原文

I am writing an ASP.Net web application. I have listview, it's datasource is a LinqDataSource. In my database, I have a staff table and I am trying filter for records by their team using a dropdownlist. This works fine, until I select "All" in the dropdownlist. It returns all staff except for the ones where the teamID is null. How can I return the records where teamID is null?

This is my code:

<asp:ListView ID="ListView1" runat="server" DataSourceID="ldsStaff" DataKeyNames="staffID">

    <LayoutTemplate>
<table>
  <tr>
     <th>Name</th>
     <th>Team</th>
  </tr>
  <tr>
     <td> </td>
     <td><asp:DropDownList ID="ddlTeamFilter" runat="server" DataSourceID="ldsTeams" DataTextField="Team" DataValueField="TeamID" AppendDataBoundItems="true" AutoPostBack="true">
        <asp:ListItem Text="[All]" Value=""></asp:ListItem>
         </asp:DropDownList>
     </td>
  </tr>
  <tr ID="itemPlaceHolder" runat="server"></tr>
</table>
</LayoutTemplate>
....
</asp:Listview>

<asp:LinqDataSource ID="ldsStaff" runat="server" 
    ContextTypeName="ProjectDatabase.ProjectDatabaseUsersDataContext" OrderBy="name" 
    TableName="Staffs" EnableUpdate="True" Where="inService == @inService && TeamID == @TeamID">
    <WhereParameters>
        <asp:Parameter DefaultValue="true" Name="inService" Type="Boolean" />
        <asp:ControlParameter ControlID="ctl00$ContentPlaceHolder1$ListView1$ddlTeamFilter" Name="TeamID" Type="Int32" PropertyName="SelectedValue"/>
     </WhereParameters>
</asp:LinqDataSource>

In my code behind I handle the LinqDataSource selecting event:

Private Sub ldsStaff_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles ldsStaff.Selecting
    Dim ddl As DropDownList = CType(ListView1.FindControlRecursive("ddlTeamFilter"), DropDownList)
    If ddl.SelectedValue = "" Then
        e.WhereParameters.Remove("TeamID")
    End If

I thought that if I removed the whereparameter when the dropdownlist is "All" it would force it to return all the records, but it doesn't work.

Please help!

Thanks,
Emma

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