我有一个应用程序，我正在寻找一个文本文件，如果对文件做了任何更改，我使用OnChanged事件处理程序来处理事件。我正在使用NotifyFilters。LastWriteTime，但是事件仍然被触发两次。这是代码。
public void Initialize()
{
FileSystemWatcher _fileWatcher = new FileSystemWatcher();
_fileWatcher.Path = "C:\\Folder";
_fileWatcher.NotifyFilter = NotifyFilters.LastWrite;
_fileWatcher.Filter = "Version.txt";
_fileWatcher.Changed += new FileSystemEventHandler(OnChanged);
_fileWatcher.EnableRaisingEvents = true;
}
private void OnChanged(object source, FileSystemEventArgs e)
{
.......
}
在我的情况下，OnChanged被调用两次，当我改变文本文件version.txt并保存它。
代码可自定义禁用阻止第二个观察者升起的时间间隔，如果他们存在，则不阻止观察者:
namespace Watcher
{
class Static
{
public static DateTime lastDomain { get; set; }
public static string lastDomainStr { get; set; }
}
public partial class Form1 : Form
{
int minMs = 20;//time for blocking in ms
public Form1()
{
InitializeComponent();
Static.lastDomain = new DateTime(1970, 1, 1, 0, 0, 0);
Static.lastDomainStr = "";
Start();
}
private void Start()//Start watcher
{
//...
domain.Changed += new FileSystemEventHandler(Domain);
domain.EnableRaisingEvents = true;
//...you second unblocked watchers
second.Changed += new FileSystemEventHandler(Second);
second.EnableRaisingEvents = true;
}
private void Domain(object source, FileSystemEventArgs e)
{
if (now.Subtract(Static.lastDomain).TotalMilliseconds < minMs && Static.lastDomainStr == e.FullPath)return;
//...you code here
/* if you need form access
this.Invoke(new MethodInvoker(() =>{ textBox1.Text = "...";}));
*/
Static.lastDomain = DateTime.Now;
Static.lastDomainStr = e.FullPath;
}
private void Second(object source, FileSystemEventArgs e)
{
//...Second rised
}
}
}
In my case need to get the last line of a text file that is inserted by other application, as soon as insertion is done. Here is my solution. When the first event is raised, i disable the watcher from raising others, then i call the timer TimeElapsedEvent because when my handle function OnChanged is called i need the size of the text file, but the size at that time is not the actual size, it is the size of the file imediatelly before the insertion. So i wait for a while to proceed with the right file size.
private FileSystemWatcher watcher = new FileSystemWatcher();
...
watcher.Path = "E:\\data";
watcher.NotifyFilter = NotifyFilters.LastWrite ;
watcher.Filter = "data.txt";
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = true;
...
private void OnChanged(object source, FileSystemEventArgs e)
{
System.Timers.Timer t = new System.Timers.Timer();
try
{
watcher.Changed -= new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = false;
t.Interval = 500;
t.Elapsed += (sender, args) => t_Elapsed(sender, e);
t.Start();
}
catch(Exception ex) {
;
}
}
private void t_Elapsed(object sender, FileSystemEventArgs e)
{
((System.Timers.Timer)sender).Stop();
//.. Do you stuff HERE ..
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = true;
}
我简单地添加了一个dupe检查如下:
private void OnChanged(object source, FileSystemEventArgs e)
{
string sTabName = Path.GetFileNameWithoutExtension(e.Name);
string sLastLine = ReadLastLine(e.FullPath);
if(sLastLine != _dupeCheck)
{
TabPage tp = tcLogs.TabPages[sTabName];
TextBox tbLog = (TextBox)tp.Controls[0] as TextBox;
tbLog.Invoke(new Action(() => tbLog.AppendText(sLastLine + Environment.NewLine)));
tbLog.Invoke(new Action(() => tbLog.SelectionStart = tbLog.Text.Length));
tbLog.Invoke(new Action(() => tbLog.ScrollToCaret()));
_dupeCheck = sLastLine;
}
}
public static String ReadLastLine(string path)
{
return ReadLastLine(path, Encoding.Default, "\n");
}
public static String ReadLastLine(string path, Encoding encoding, string newline)
{
int charsize = encoding.GetByteCount("\n");
byte[] buffer = encoding.GetBytes(newline);
using (FileStream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
long endpos = stream.Length / charsize;
for (long pos = charsize; pos < endpos; pos += charsize)
{
stream.Seek(-pos, SeekOrigin.End);
stream.Read(buffer, 0, buffer.Length);
if (encoding.GetString(buffer) == newline)
{
buffer = new byte[stream.Length - stream.Position];
stream.Read(buffer, 0, buffer.Length);
return encoding.GetString(buffer);
}
}
}
return null;
}
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern int SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);
private const int WM_VSCROLL = 0x115;
private const int SB_BOTTOM = 7;
/// <summary>
/// Scrolls the vertical scroll bar of a multi-line text box to the bottom.
/// </summary>
/// <param name="tb">The text box to scroll</param>
public static void ScrollToBottom(TextBox tb)
{
SendMessage(tb.Handle, WM_VSCROLL, (IntPtr)SB_BOTTOM, IntPtr.Zero);
}
