C# 使用 LinQ 从组合框选择中过滤列表框

Question

我有一个名为 lstTickets 的列表框和一个名为 cboFilter 的组合框。我正在尝试根据组合框中的 ticket.District 过滤列表框中的项目。因此，例如，如果我从组合框中选择，是列表框中唯一的团队。任何帮助表示赞赏。

 List<Ticket> = new List<Ticket>()
    {
        new Ticket { Name = "Arsenal", Badge = "images/arsenal.jpg", Price = 900, Stadium = "emirates.jpg", District = "London" },
        new Ticket { Name = "Tottenham Hotspur", Badge = "images/tottenham.jpg", Price = 850, Stadium = "tottenham.jpg", District = "" },
        new Ticket { Name = "Manchester United", Badge = "images/.png", Price = 1000, Stadium = "oldtrafford.jpg", District = "" },
    };

 private void cboFilter_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
       var query = from Ticket in tickets where cboFilter.SelectedItem.ToString() == Ticket.District select Ticket;

        lstTickets.ItemsSource = null;
        lstTickets.Items.Clear();

        List<Ticket> tmp = new List<Ticket>();

        foreach (var tickets in query)
        {
            tmp.Add(tickets);

        }
        lstTickets.ItemsSource = tmp;

    }



                        <Image Width="200" Height="150" HorizontalAlignment="Left" Source="{x:Bind Badge }" />
                        <TextBlock FontSize="22" HorizontalAlignment="Left" Text="{x:Bind Name}" Style="{StaticResource HeaderTextBlockStyle}"/>
                        <TextBlock FontSize="16" HorizontalAlignment="Left"> € <Run Text="{Binding Price}" /></TextBlock>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

编辑：在 mainpage.cs 中填充组合框

private void myGrid_Loaded(object sender, RoutedEventArgs e)
    {
    }

Answer 1

看起来 ToString() 对所选项目不起作用。

var searchTerm=  cboFilter.SelectedItem.ToString();
var query = from Ticket in tickets where Ticket.District == term  select Ticket;

确保在搜索词处设置断点以查看其是否正确

但我想我知道你的问题，所选项目将返回整个对象，所以请执行以下操作

var selectedTicked=  cboFilter.SelectedItem as Ticket;
var searchTerm= selectedTicket.District 
    var query = from Ticket in tickets where Ticket.District == term  select Ticket;

Answer 2

尝试首先检查您在 cboFilter.SelectedItem 中有一个实际值，然后如果您使用小写比较这些值。我更喜欢使用 System.Linq，所以我修改了您的查询以使用它：

private void cboFilter_SelectionChanged(object sender, SelectionChangedEventArgs e)
{

   var comboBoxItem = cboFilter.SelectedItem as ComboBoxItem;

   if(comboBoxItem == null) return; // or log an error here or something if it should not be empty.

   var query = tickets.Where(t => t.District.ToLower() == comboBoxItem.Content.ToString().ToLower());

    lstTickets.ItemsSource = null;
    lstTickets.Items.Clear();

    List<Ticket> tmp = new List<Ticket>();

    foreach (var tickets in query)
    {
        tmp.Add(tickets);

    }
    lstTickets.ItemsSource = tmp;

}