咨询区
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Homam：
我先说一下我的顾虑，是这样的，我有一个 windows service 服务在不断的写入日志，同时我还有个看板程序在不断的获取 windows service 程序写入的日志。
问题是：service 程序在写日志的时候会 lock 文件，看板程序在读取的时候也会 lock 文件，这就很尴尬了，经常遇到进程被占用的异常。.
服务程序代码：
void WriteInLog(string logFilePath, data)
{
File.AppendAllText(logFilePath, string.Format("{0} : {1}\r\n", DateTime.Now, data));
}
看板程序代码：
int index = 0;
private void Form1_Load(object sender, EventArgs e)
{
try
{
using (StreamReader sr = new StreamReader(logFilePath))
{
while (sr.Peek() >= 0) // reading the old data
{
AddLineToGrid(sr.ReadLine());
index++;
}
sr.Close();
}
timer1.Start();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void timer1_Tick(object sender, EventArgs e)
{
using (StreamReader sr = new StreamReader(logFilePath))
{
// skipping the old data, it has read in the Form1_Load event handler
for (int i = 0; i < index ; i++)
sr.ReadLine();
while (sr.Peek() >= 0) // reading the live data if exists
{
string str = sr.ReadLine();
if (str != null)
{
AddLineToGrid(str);
index++;
}
}
sr.Close();
}
}
请问大家我该如何解决此问题？
回答区
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Manfred：
你的问题在于写入和读取都是以排他的方式进行，其实 FileStream 中是可以支持共享的方式进行读写的。
比如将 service 代码改造如下：
var outStream = new FileStream(logfileName, FileMode.Open,
FileAccess.Write, FileShare.ReadWrite);
看板程序改造如下：
var inStream = new FileStream(logfileName, FileMode.Open,
FileAccess.Read, FileShare.ReadWrite);
用完的时候记得 Close 一下，对了， FileStream 实现了 IDisposable 接口，可以用 using 包一下，参考如下代码：
using(var outStream = ...)
{
// using outStream here
...
}
点评区
我特意看了下 FileStream 的 FileShare.ReadWrite 参数解释。
[ComVisible(true)]
[Flags]
public enum FileShare
{
None = 0,
Read = 1,
Write = 2,
//
// Summary:
// Allows subsequent opening of the file for reading or writing. If this flag is
// not specified, any request to open the file for reading or writing (by this process
// or another process) will fail until the file is closed. However, even if this
// flag is specified, additional permissions might still be needed to access the
// file.
ReadWrite = 3,
Delete = 4,
Inheritable = 16
}
我去，原来还可以这样玩，对 FileStream 用的还不透彻，学习了。
