跟踪监听器写入文本框（WPF应用程序）

Question

对于我的WPF应用程序，我使用TextWriterTraceListener记录到文本文件。我怎样才能将Trace输出显示到文本框？

Answer 1

我用这个C＃的WinForms，应该很容易调整到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); 
    } 
} 

使用它像

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

记住跟踪/ Debug.Listeners.Remove（debugListener）;当你不再需要它时。

Answer 2

您可以附加一个自定义侦听器，它更新Textbox.Text属性。 因此，您需要从抽象基类TraceListener继承并重写TraceData，TraceEvent，TraceTransfer方法之一。

Answer 3

如何实现一个自定义的TraceListener，只需将跟踪消息附加到字符串？然后将该字符串作为属性公开，实现INotifyPropertyChanged并将TextBox控件绑定到该属性。

事情是这样的：

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); 
     } 
    } 
} 

你需要这个的TraceListener添加到活动监听器的列表：

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

Answer 4

下面的代码是@Mark Seemann代码的C＃6.0风格。

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，结合TraceOutput属性为文本框。如果您希望文本框随累积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，事件处理程序简单如下。

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