请教下面的代码！

Pavel_d 2009-05-13 09:57:39



using System;



using System.Collections.Generic;



using System.Text;



using System.Management;



using System.Net;



namespace testPrintJobArrival



{



public delegate void PrintJobArrived(object sender, ManagementBaseObject printProperties);



public class WMIPrinter



{



ConnectionOptions _co = new ConnectionOptions();



internal static System.Management.ManagementScope _ms = null;



private const string PRINTERJOBS = "SELECT * FROM Win32_PrintJob";



private const string PRINTERS = "SELECT * FROM Win32_Printer";



private const int QUERYINTERVAL = 1;



public PrintJobArrived OnPrintJobArrived = null;



private System.Management.ManagementEventWatcher _printEventWatcher = null;



private ManagementObjectSearcher _moSearchPrintJobs = null;



public WMIPrinter()



{ 



//Point to machine



_co.EnablePrivileges = true;



_co.Impersonation = ImpersonationLevel.Delegate;



_ms = new System.Management.ManagementScope("\\\\localhost\\root\\cimv2", _co);



_moSearchPrintJobs = new ManagementObjectSearcher(PRINTERJOBS);



}



public void StartPrintWatcher()



{



_printEventWatcher = new System.Management.ManagementEventWatcher();



_printEventWatcher.Query = new System.Management.EventQuery("SELECT * FROM 



__InstanceCreationEvent WITHIN " + QUERYINTERVAL + " WHERE TargetInstance ISA \"Win32_PrintJob\"");



string hostName = Dns.GetHostName();



this._printEventWatcher.Scope = new System.Management.ManagementScope("\\\\" + hostName + "\\root\\CIMV2");



_printEventWatcher.EventArrived += new EventArrivedEventHandler(this.Arrived);



 



_printEventWatcher.Start(); //asynchronous



//_printEventWatcher.WaitForNextEvent(); //synchronous



}



public void StopPrintWatcher()



{



if (_printEventWatcher != null)



_printEventWatcher.Stop();



}



/// <summary>



/// new Print Job has Arrived...



/// </summary>



/// <param name="sender"></param>



/// <param name="e"></param>



public void Arrived(object sender, EventArrivedEventArgs e)



{



foreach (PropertyData pd in e.NewEvent.Properties)



{



ManagementBaseObject mbo = pd.Value as ManagementBaseObject;



if (mbo != null)



{



//mbo.Properties[""]



if (OnPrintJobArrived != null)



OnPrintJobArrived(this, mbo);



}



}



}



}



}

上面delegate 的使用有问题！

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Pavel_d 2009-05-13

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OnPrintJobArrived(this, mbo);
[这里是怎么调用的，请解释一下？？

Pavel_d 2009-05-13

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_printEventWatcher.EventArrived += new EventArrivedEventHandler(this.Arrived);
在Arrived函数中



public void Arrived(object sender, EventArrivedEventArgs e)



{

   foreach (PropertyData pd in e.NewEvent.Properties)

   {

       ManagementBaseObject mbo = pd.Value as ManagementBaseObject;

       if (mbo != null)

       {

          if (OnPrintJobArrived != null)

          OnPrintJobArrived(this, mbo);    

          这里是怎么调用的，请解释一下？？

       }

   }

}