如何收集所有系统事件日志并将其保存到文件中

我正在尝试使用此函数：

public void DoBackup(string sLogName)
{
    string sBackup = sLogName;  // could be for example "Application"
    EventLog log = new EventLog();
    log.Source = sBackup;
    var query = from EventLogEntry entry in log.Entries
                orderby entry.TimeGenerated descending
                select entry;
    string sBackupName = sBackup + "Log";
    var xml = new XDocument(
        new XElement(sBackupName,
            from EventLogEntry entry in log.Entries
            orderby entry.TimeGenerated descending
            select new XElement("Log",
              new XElement("Message", entry.Message),
              new XElement("TimeGenerated", entry.TimeGenerated),
              new XElement("Source", entry.Source),
              new XElement("EntryType", entry.EntryType.ToString())
            )
          )
        );
    DateTime oggi = DateTime.Now;
    string sToday = DateTime.Now.ToString("yyyyMMdd_hhmmss");
    string path = String.Format("{0}_{1}.xml", sBackupName, sToday);
    xml.Save(Path.Combine(Environment.CurrentDirectory, path));
}

一般来说，我想创建两个文件：

1. 所有应用程序事件日志的文本文件
2. 所有系统事件日志的文本文件

我这样调用这个函数：

DoBackup（"测试"）；但当运行它时，我在上得到了一个异常

var xml = new XDocument(
    new XElement(sBackupName,
        from EventLogEntry entry in log.Entries
        orderby entry.TimeGenerated descending
        select new XElement("Log",
          new XElement("Message", entry.Message),
          new XElement("TimeGenerated", entry.TimeGenerated),
          new XElement("Source", entry.Source),
          new XElement("EntryType", entry.EntryType.ToString())
        )
      )
    );

尚未指定日志属性值

System.ArgumentException was unhandled
  HResult=-2147024809
  Message=Log property value has not been specified.
  Source=System
  StackTrace:
       at System.Diagnostics.EventLogInternal.OpenForRead(String currentMachineName)
       at System.Diagnostics.EventLogInternal.GetEntryAtNoThrow(Int32 index)
       at System.Diagnostics.EventLogEntryCollection.EntriesEnumerator.MoveNext()
       at System.Linq.Enumerable.<CastIterator>d__b1`1.MoveNext()
       at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
       at System.Linq.OrderedEnumerable`1.<GetEnumerator>d__0.MoveNext()
       at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
       at System.Xml.Linq.XContainer.AddContentSkipNotify(Object content)
       at System.Xml.Linq.XElement..ctor(XName name, Object content)
       at Diagnostic_Tool_Blue_Screen.Form1.DoBackup(String sLogName) in d:'C-Sharp'Diagnostic Tool Blue Screen'Diagnostic Tool Blue Screen'Diagnostic Tool Blue Screen'Form1.cs:line 161
       at Diagnostic_Tool_Blue_Screen.Form1.Diagnose_Click(Object sender, EventArgs e) in d:'C-Sharp'Diagnostic Tool Blue Screen'Diagnostic Tool Blue Screen'Diagnostic Tool Blue Screen'Form1.cs:line 57
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at Diagnostic_Tool_Blue_Screen.Program.Main() in d:'C-Sharp'Diagnostic Tool Blue Screen'Diagnostic Tool Blue Screen'Diagnostic Tool Blue Screen'Program.cs:line 19
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

---

最后，我硬盘上文本文件的内容应该是这样的：

Event[0]:
  Log Name: System
  Source: EventLog
  Date: 2013-01-17T03:19:18.000
  Event ID: 6011
  Task: N/A
  Level: Information
  Opcode: N/A
  Keyword: Classic
  User: N/A
  User Name: N/A
  Computer: windows-uj49s6b
  Description: 
The NetBIOS name and DNS host name of this machine have been changed from WINDOWS-UJ49S6B to WIN-F1MN9CTN28S.
Event[1]:
  Log Name: System

EventApp文本文件为18mb，EventSys文本文件约为3mb。

if (!EventLog.Exists(sLogName))
     return; // or show error message
// build xml
EventLog log = new EventLog(sLogName); // specify log name
var xml = new XDocument(
    new XElement(sLogName,
        from EventLogEntry entry in log.Entries
        orderby entry.TimeGenerated descending
        select new XElement("Log",
          new XElement("Message", entry.Message),
          new XElement("TimeGenerated", entry.TimeGenerated),
          new XElement("Source", entry.Source),
          new XElement("EntryType", entry.EntryType.ToString())
        )
    ));