跟踪侦听器以写入文本框（WPF 应用程序）

Question

对于我的 WPF 应用程序，我使用 TextWriterTraceListener 将日志记录到文本文件。如何将 Trace 输出也显示到文本框？

Answer 1

我将它用于 C# winforms，应该可以轻松调整为 wpf

public class MyTraceListener : TraceListener
{
    private TextBoxBase output;

    public MyTraceListener(TextBoxBase output) {
        this.Name = "Trace";
        this.output = output;
    }


    public override void Write(string message) {

        Action append = delegate() {
            output.AppendText(string.Format("[{0}] ", DateTime.Now.ToString()));
            output.AppendText(message); 
        };
        if (output.InvokeRequired) {
            output.BeginInvoke(append);
        } else {
            append();
        }

    }

    public override void WriteLine(string message) {
        Write(message + Environment.NewLine);
    }
}

像这样使用它

TraceListener debugListener = new MyTraceListener (theTextBox);
Debug.Listeners.Add(debugListener);
Trace.Listeners.Add(debugListener);

记得 Trace/Debug.Listeners.Remove(debugListener);当你不再需要它时。

Answer 2

如何实现一个自定义 TraceListener，它只是将跟踪消息附加到一个字符串？然后将该字符串公开为属性，实现 INotifyPropertyChanged 并将 TextBox 控件数据绑定到该属性。

类似这样的：

public class MyTraceListener : TraceListener, INotifyPropertyChanged
{
    private readonly StringBuilder builder;

    public MyTraceListener()
    {
        this.builder = new StringBuilder();
    }

    public string Trace
    {
        get { return this.builder.ToString(); }
    }

    public override void Write(string message)
    {
        this.builder.Append(message);
        this.OnPropertyChanged(new PropertyChangedEventArgs("Trace"));
    }

    public override void WriteLine(string message)
    {
        this.builder.AppendLine(message);
        this.OnPropertyChanged(new PropertyChangedEventArgs("Trace"));
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, e);
        }
    }
}

您需要将此 TraceListener 添加到活动侦听器列表中：

Trace.Listeners.Add(new MyTraceListener());

Answer 3

下面的代码是@Mark Seemann 的C#6.0 风格的代码。

public class MyTraceListener : TraceListener, INotifyPropertyChanged
{
    private readonly StringBuilder _builder;

    public MyTraceListener()
    {
        _builder = new StringBuilder();
    }

    public string Trace => _builder.ToString();

    public override void Write(string message)
    {
        _builder.Append(message);
        OnPropertyChanged(new PropertyChangedEventArgs("Trace"));
    }

    public override void WriteLine(string message)
    {
        _builder.AppendLine(message);
        OnPropertyChanged(new PropertyChangedEventArgs("Trace"));
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        PropertyChanged?.Invoke(this, e);
    }
}

假设 MainViewModel 是 MainWindow.xaml 文件的根 DataContext。要以 MVVM 方式应用 MyTraceListener，请在 MainViewModel.cs 中编写以下代码。

private string _traceOutput;
private readonly MyTraceListener _trace = new MyTraceListener();

// Constructor
public MainViewModel() {

    // ...your viewmodel initialization code.

    // Add event handler in order to expose logs to MainViewModel.TraceOutput property.
    WeakEventManager<INotifyPropertyChanged, PropertyChangedEventArgs>.AddHandler(_trace, "PropertyChanged", traceOnPropertyChanged);
    Trace.Listeners.Add(_trace);
}

private void traceOnPropertyChanged(object sender, PropertyChangedEventArgs e)
{
    if (e.PropertyName == "Trace")
        TraceOutput = _trace.Trace;
}

public string TraceOutput
{
    get { return _traceOutput; }
    set {
        _traceOutput = value;
        RaisePropertyChanged(); // This method is from Mvvm-light.
    }
}

在 MainWindow.xaml 中，将 TraceOutput 属性绑定到 TextBox。如果您希望 TextBox 连同累积的日志一起滚动到底部，请应用 TextChanged 事件。

<TextBox x:Name="TextBoxLog" TextWrapping="Wrap" Text="{Binding TraceOutput}" VerticalScrollBarVisibility="Auto" AcceptsReturn="True" TextChanged="TextBoxLog_OnTextChanged" />

在 XAML 文件 (MainWindow.xaml.cs) 的代码隐藏中，事件处理程序如下所示。

    private void TextBoxLog_OnTextChanged(object sender, TextChangedEventArgs e)
    {
        TextBoxLog.ScrollToEnd();
    }

Answer 4

您可以附加一个自定义侦听器来更新 Textbox.Text 属性。 因此，您需要从抽象基类 TraceListener 继承并覆盖 TraaceData、TraceEvent、TraceTransfer 方法之一。