[C#]如何使用TraceListener實作類似Visual Studio的輸出視窗

前陣子花了點時間在為開發中的產品加強除錯的功能,想要讓開發上發生的問題能直接在產品上就一目而然的看到,而不用另行開啟DebugView或是Log來看。簡單地說想要為產品加上類似是Visual Studio的輸出視窗,或者是DebugView類似的功能,能夠很即時的偵測並顯示出系統發出的Debug或是Trace訊息。為了達到這個需求,筆者用內建的TraceListener簡單的試做了一下,這篇隨手紀錄一下。

要達到類似DebugView的效果,代表著我們必須要能擷取到Debug.WriteLine或是Trace.WriteLine的訊息,為此我們必須要建立一個TraceListener,繼承自DefaultTraceListener,並覆寫它的WriteLine方法。在覆寫的WriteLine方法中我們可以將收到的訊息做些處理,像是把它顯示到ListBox之類的。

    public class ListBoxLogTraceListener : DefaultTraceListener
{
private ListBox m_ListBox { get; set; }

/// <summary>
/// Initializes a new instance of the <see cref=”ListBoxLogTraceListener”/> class.
/// </summary>
/// <param name=”listBox”>The list box.</param>
public ListBoxLogTraceListener(ListBox listBox)
{
m_ListBox = listBox;
}

/// <summary>
/// Writes the output to the OutputDebugString function and to the <see cref=”M:System.Diagnostics.Debugger.Log(System.Int32,System.String,System.String)”/> method, followed by a carriage return and line feed (\r\n).
/// </summary>
/// <param name=”message”>The message to write to OutputDebugString and <see cref=”M:System.Diagnostics.Debugger.Log(System.Int32,System.String,System.String)”/>.</param>
/// <PermissionSet>
/// <IPermission class=”System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089” version=”1” Unrestricted=”true”/>
/// <IPermission class=”System.Security.Permissions.SecurityPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089” version=”1” Flags=”ControlEvidence”/>
/// </PermissionSet>
public override void WriteLine(string message)
{
if (!m_ListBox.Visible)
return;

if (m_ListBox.InvokeRequired)
{
m_ListBox.BeginInvoke(new MethodInvoker(
delegate { WriteLine(message); }
));
return;
}

m_ListBox.Items.Add(string.Format(“{0}\t{1}”, DateTime.Now, message));
}
}


TraceListener類別撰寫完畢,可以透過Debug.Listeners.Add或是Trace.Listeners.Add將撰寫的TraceListener類別加入,當我們程式中有用到Debug.WriteLine或是Trace.WriteLine時就會連帶觸發我們撰寫的TraceListener,藉此滿足我們想要達到的效果。


//Debug.Listeners.Add(new ListBoxLogTraceListener(listBox1));
Trace.Listeners.Add(new ListBoxLogTraceListener(listBox1));

Debug.WriteLine(“Debug msg…”);

Trace.WriteLine(“Trace msg…”);

這邊附上較為完整的測試範例:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication6
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
//Debug.Listeners.Add(new ListBoxLogTraceListener(listBox1));
Trace.Listeners.Add(new ListBoxLogTraceListener(listBox1));
}

private void button1_Click(object sender, EventArgs e)
{
Debug.WriteLine(“Debug msg…”);
}

private void button2_Click(object sender, EventArgs e)
{
Trace.WriteLine(“Trace msg…”);
}
}

public class ListBoxLogTraceListener : DefaultTraceListener
{
private ListBox m_ListBox { get; set; }

/// <summary>
/// Initializes a new instance of the <see cref=”ListBoxLogTraceListener”/> class.
/// </summary>
/// <param name=”listBox”>The list box.</param>
public ListBoxLogTraceListener(ListBox listBox)
{
m_ListBox = listBox;
}

/// <summary>
/// Writes the output to the OutputDebugString function and to the <see cref=”M:System.Diagnostics.Debugger.Log(System.Int32,System.String,System.String)”/> method, followed by a carriage return and line feed (\r\n).
/// </summary>
/// <param name=”message”>The message to write to OutputDebugString and <see cref=”M:System.Diagnostics.Debugger.Log(System.Int32,System.String,System.String)”/>.</param>
/// <PermissionSet>
/// <IPermission class=”System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089” version=”1” Unrestricted=”true”/>
/// <IPermission class=”System.Security.Permissions.SecurityPermission, mscorlib, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b77a5c561934e089” version=”1” Flags=”ControlEvidence”/>
/// </PermissionSet>
public override void WriteLine(string message)
{
if (!m_ListBox.Visible)
return;

if (m_ListBox.InvokeRequired)
{
m_ListBox.BeginInvoke(new MethodInvoker(
delegate { WriteLine(message); }
));
return;
}

m_ListBox.Items.Add(string.Format(“{0}\t{1}”, DateTime.Now, message));
}
}
}

運行起來我們可以看到它能偵測並顯示系統發出的Debug或是Trace訊息,在產品的除錯上會方便許多。

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