跟蹤監聽器寫入文本框（WPF應用程序）

Question

對於我的WPF應用程序，我使用TextWriterTraceListener記錄到文本文件。我怎樣才能將Trace輸出顯示到文本框？

Answer 1

我用這個C＃的WinForms，應該很容易調整到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); 

記住跟蹤/ Debug.Listeners.Remove（debugListener）;當你不再需要它時。

Answer 2

您可以附加一個自定義偵聽器，它更新Textbox.Text屬性。 因此，您需要從抽象基類TraceListener繼承並重寫TraceData，TraceEvent，TraceTransfer方法之一。

Answer 3

如何實現一個自定義的TraceListener，只需將跟蹤消息附加到字符串？然後將該字符串作爲屬性公開，實現INotifyPropertyChanged並將TextBox控件綁定到該屬性。

事情是這樣的：

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); 
     } 
    } 
} 

你需要這個的TraceListener添加到活動監聽器的列表：

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

Answer 4

下面的代碼是@Mark Seemann代碼的C＃6.0風格。

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); 
    } 
} 

假設MainViewModel是MainWindow.xaml文件的根DataContext。要以MVVM方式應用MyTraceListener，請在MainViewModel.cs中編寫以下代碼。

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，結合TraceOutput屬性爲文本框。如果您希望文本框隨累積日誌一起滾動到底部，請應用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）的代碼隱藏中，事件處理程序簡單如下。

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