將可觀察的集合綁定到ListView WPF

Question

我正在為工作的電子郵件客戶端，但是我無法將可觀察的集合以正確的方式綁定到我的列表視圖。 請提出建議，因為我無法在線找到確切的問題

C＃

public partial class Mail : UserControl
{
    ObservableCollection<GetMails> BindMe = new ObservableCollection<GetMails>();
    public Mail()
    {
        InitializeComponent();
    }

    private void Grid_Loaded_1(object sender, RoutedEventArgs e)
    {
        BindMe = FetchAllHeaders(server, port, false, username, password);
        lstMail.ItemsSource = BindMe.ToList();
    }

    private ObservableCollection<GetMails> FetchAllHeaders(string hostname, int port, bool useSsl, string username, string password)
    {
        // The client disconnects from the server when being disposed
        using (Pop3Client client = new Pop3Client())
        {
            GetMails gm = new GetMails();

            // Connect to the server
            client.Connect(hostname, port, useSsl);

            // Authenticate ourselves towards the server
            client.Authenticate(username, password);

            // Get the number of messages in the inbox
            int messageCount = client.GetMessageCount();

            // We want to download all messages
            ObservableCollection<GetMails> getHeaders = new ObservableCollection<GetMails>();

            // Messages are numbered in the interval: [1, messageCount]
            // Ergo: message numbers are 1-based.
            // Most servers give the latest message the highest number
            for (int i = messageCount; i > 0; i--)
            {
                MessageHeader headers = client.GetMessageHeaders(i);
                RfcMailAddress from = headers.From;
                Message message = client.GetMessage(i);
                gm.Header = client.GetMessageHeaders(i).Subject;
                gm.From = from.MailAddress.ToString();
                int count = 0;
                foreach (MessagePart attachment in message.FindAllAttachments())
                {
                    count++; 
                }
                gm.NumberAttach = count;
                getHeaders.Add(gm);
            }


            // Now return the fetched messages
            return getHeaders;
        }
    }
}

XAML

<UserControl x:Class="VeriMail.Mail"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid Loaded="Grid_Loaded_1" Margin="0,0,-132,0">
    <ListView x:Name="lstMail" Height="399" VerticalAlignment="Top" Margin="0,0,-67,-99" ScrollViewer.HorizontalScrollBarVisibility="Visible" ScrollViewer.VerticalScrollBarVisibility="Disabled" ScrollViewer.CanContentScroll="True">
        <ListView.View>
            <GridView>
                <GridViewColumn Width="140" Header="Subject" />
                <GridViewColumn Width="140" Header="From" />
                <GridViewColumn Width="140" Header="Number of Attachments"/>
            </GridView>
        </ListView.View>
    </ListView>

</Grid>

當我這樣做時得到的輸出就是VeriMail.GetMail

如果我將gridview更改為此：

<GridViewColumn Width="140" Header="Subject" DisplayMemberBinding="{Binding Header}"/>
<GridViewColumn Width="140" Header="From" DisplayMemberBinding="{Binding From}"/>
<GridViewColumn Width="140" Header="Number of Attachments" DisplayMemberBinding="{Binding NumberAttach}"/>

然后，輸出更改為我想要的信息，但它將復制一封電子郵件，最后一封電子郵件插入可觀察的集合中。

Answer 1

UPDATE ：問題是當您調用ToList ，集合被復制，並且將來不會反映更改。 刪除該方法調用，它應該可以工作。

但是，最好在XAML中綁定ItemsSource而不是在后面的代碼中進行綁定：

<ListView x:Name="lstMail" ItemsSource="{Binding BindMe, RelativeSource={RelativeSource AncestorType=UserControl}}" Height="399" VerticalAlignment="Top" Margin="0,0,-67,-99" ScrollViewer.HorizontalScrollBarVisibility="Visible" ScrollViewer.VerticalScrollBarVisibility="Disabled" ScrollViewer.CanContentScroll="True">
    <ListView.View>
        <GridView>
            <GridViewColumn Width="140" Header="Subject" />
            <GridViewColumn Width="140" Header="From" />
            <GridViewColumn Width="140" Header="Number of Attachments"/>
        </GridView>
    </ListView.View>
</ListView>

並且也不要在FetchAllHeaders()更改BindMe集合引用本身，而是修改其內容。 否則，綁定將不起作用，因為再次更改了引用。

Answer 2

如另一個答案中所述，綁定到XAML是一種通常的做法（例如，使用MVVM模式）。 如果這樣做，您可能已經找到了該錯誤...

lstMail.ItemsSource = BindMe.ToList();

調用ToList()將創建一個全新的List<GetMails>其中包含可觀察集合的內容。 當您添加新項目時，列表不會更改-它是副本，對原始集合一無所知。

嘗試

lstMail.ItemsSource = BindMe;

這應該可以解決您的問題。

Answer 3

lstMail.ItemsSource = BindMe.ToList();

應該

lstMail.ItemsSource = BindMe;

綁定到列表不同於綁定到ObservableCollection。 可觀察集合是用於綁定的對象，因為它實現了ICollectionChanged。 清單沒有。