在文本框[WPF]中动态显示文件内容

我无法再现您的确切问题,我得到的问题是文本文件中只有新文本出现。这是因为StreamReader是一个成员变量,它是一个仅转发的读取器。您可以通过执行以下操作来解决此问题:

public string Read()
{
    using (var stream = new FileStream(@"chat.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
    {
        using (var reader = new StreamReader(stream))
        {
            string tmp = "";
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                tmp += line + '\n';
            }
            return tmp;
        }
    }
}

编辑:问题进一步澄清后:

XAML:

<Grid>

    <Grid.ColumnDefinitions>
        <ColumnDefinition></ColumnDefinition>
        <ColumnDefinition></ColumnDefinition>
    </Grid.ColumnDefinitions>

    <Grid.RowDefinitions>
        <RowDefinition Height="*"></RowDefinition>
    </Grid.RowDefinitions>

    <DockPanel Grid.Column="0" LastChildFill="True">
        <Label DockPanel.Dock="Top">IRC channel simulator</Label>
        <Button DockPanel.Dock="Top" Click="Button_Click">Send Chat</Button>
        <ScrollViewer HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Visible">
            <TextBox Background="AliceBlue" AcceptsReturn="True" Margin="0,0,0,0" TextWrapping="Wrap" Name="chatWriter" IsReadOnlyCaretVisible="false" />
        </ScrollViewer>
    </DockPanel>

    <ScrollViewer Grid.Column="1" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Visible">
        <TextBox IsReadOnly="true" Margin="0,0,0,0" TextWrapping="Wrap" Name="chat" IsReadOnlyCaretVisible="false"/>
    </ScrollViewer>
</Grid>

Xaml背后的代码:

public partial class MainWindow : Window
{
    ChatHandler chatHandler;
    BackgroundWorker worker;

    public MainWindow()
    {
        InitializeComponent();

        chatHandler = new ChatHandler();

        worker = new BackgroundWorker();
        worker.WorkerSupportsCancellation = true;
        worker.DoWork += new DoWorkEventHandler(run);
    }

    private void write(string text)
    {
        if (chat.Text != text && text != "")
        {
            chat.Text = text;
        }
    }

    private void run(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker bg = sender as BackgroundWorker;
        while (!bg.CancellationPending)
        {
            chat.Dispatcher.BeginInvoke((Action)(() => {
                write(chatHandler.Read());
            }));
            Thread.Sleep(100);
        }
    }

    private void chat_Loaded(object sender, RoutedEventArgs e)
    {
        if (!worker.CancellationPending)
        {
            worker.RunWorkerAsync();
        }
    }

    private void chat_Unloaded(object sender, RoutedEventArgs e)
    {
        worker.CancelAsync();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        chatHandler.Write(chatWriter.Text);
    }
}

聊天处理程序

public class ChatHandler
{
    public FileStream stream;
    //StreamWriter writer;
    //StreamReader reader;

    public ChatHandler()
    {
        stream = new FileStream(@"chat.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite);
        //writer = new StreamWriter(stream);
        //reader = new StreamReader(stream);
    }

    public void Write(string line)
    {
        using (var fileStream = new FileStream(@"chat.txt", FileMode.Append, FileAccess.Write, FileShare.ReadWrite))
        {
            using (var writer = new StreamWriter(fileStream))
            {
                writer.WriteLineAsync(line);
                writer.Flush();
            }
        }
    }

    public string Read()
    {
        using (var fileStream = new FileStream(@"chat/" + DateTime.Today.ToString("d") + ".txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
        {
            using (var reader = new StreamReader(fileStream))
            {
                string tmp = "";
                string line;
                while ((line = reader.ReadLine()) != null)
                {
                    tmp += line + '\n';
                }
                return tmp;
            }
        }
    }
}