//Class-level declaration.
 /* Create a TraceSwitch to use in the entire application.*/
 static TraceSwitch mySwitch = new TraceSwitch("General", "Entire Application");
 
 static public void MyMethod() {
    // Write the message if the TraceSwitch level is set to Error or higher.
    if(mySwitch.TraceError)
       Console.WriteLine("My error message.");
 
    // Write the message if the TraceSwitch level is set to Verbose.
    if(mySwitch.TraceVerbose)
       Console.WriteLine("My second error message.");
 }
 
 public static void Main(string[] args) {
    // Run the method that prints error messages based on the switch level.
    MyMethod();
 }

private static TraceSwitch appSwitch = new TraceSwitch("mySwitch",
    "Switch in config file");

public static void Main(string[] args)
{
    //...
    Console.WriteLine("Trace switch {0} configured as {1}",
    appSwitch.DisplayName, appSwitch.Level.ToString());
    if (appSwitch.TraceError)
    {
        //...
    }
}

//引入命名空间
using System;
using System.Diagnostics;

class TracingExample
{
  static void Main(string[] args)
  {
    TraceSwitch General = new TraceSwitch("General", "Application Switch");

    Trace.WriteLineIf(General.TraceError, "General - Error Tracing Enabled");
    Trace.WriteLineIf(General.TraceWarning, "General - Warning Tracing Enabled");
    Trace.WriteLineIf(General.TraceInfo, "General - Info Tracing Enabled");
    Trace.WriteLineIf(General.TraceVerbose, "General - Verbose Tracing Enabled");

  }
}


/*
<?xml version="1.0" encoding="utf-8" ?> 
<configuration>
    <system.diagnostics>
        <switches>
            <add name="General" value="1" />

        </switches>
    </system.diagnostics>
</configuration>
*/