C# check file that used by process

Question

Let i have program that open file and append something. If i should run two apllication i will get IOException file used by another process. How it's possible to check that file Log.txt is using by another process?

class Program
{
    static void Main(string[] args)
    {
        FileInfo file = new FileInfo(@"D:\Log.txt");
        using (StreamWriter sw = file.AppendText())
        {
            for (int i = 0; i < 1000; i++)
            {
                System.Threading.Thread.Sleep(100);
                sw.WriteLine("Hello");
                sw.WriteLine("And");
                sw.WriteLine("Welcome");
            }
            Console.WriteLine("The work is done");
        }
    }
}

Answer 1

You should try to open and write to the file. If it is in use you get an exception. No other way in .NET.

protected virtual bool IsFileLocked(FileInfo file)
{
    FileStream stream = null;

    try
    {
        stream = file.Open(FileMode.Open, FileAccess.Read, FileShare.None);
    }
    catch (IOException)
    {
        //the file is unavailable because it is:
        //still being written to
        //or being processed by another thread
        //or does not exist (has already been processed)
        return true;
    }
    finally
    {
        if (stream != null)
            stream.Close();
    }

    //file is not locked
    return false;
}