System.IO.IOException: The process cannot access the file '.txt' because it is being used by another process

Question

I am using the next code to log errors of an web application.

using (StreamWriter myStream = new StreamWriter(sLogFilePath, true))
{                
myStream.WriteLine(string.Format("{0, -45}{1, -25}{2, -10 {3}", guid, DateTime.Now, StringEnum.GetStringValue(enumMsg), sText));      

}

Sometimes, the following exception 'System.IO.IOException: The process cannot access the file '.txt' because it is being used by another process.' is thrown.

I think this is caused by multiple instances of the web app at the same time. Can you help me fix this problem, please ?

EDIT: I have to add that for every method I log like this:

Date - Method X started.

Date - Exception.Message (table not found or other errors)

Date - Method X stopped.

and when this Error appears, it's logged only this:

Date - System.IO.IOException: The process cannot access the file '.txt' because it is being used by another process.

Answer 1

I've added this code to my class:

 public static bool IsFileLocked(FileInfo file)
        {
            FileStream stream = null;

            try
            {
                stream = file.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
            }
            catch
            {
                return true;
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                }
            }

            return false;
        }

and now my LogToFile method is like this:

while (IsFileLocked(fi))
            {
            }

            using (StreamWriter myStream = new StreamWriter(sLogFilePath, true))
            {
                if (displayTime == true)
                    myStream.WriteLine(string.Format("{0, -45}{1, -25}{2, -10}{3}", guid, DateTime.Now, StringEnum.GetStringValue(enumMsg), sText));
                else
                    myStream.WriteLine(string.Format("{0, -70}{1, -10}{2} ", guid, StringEnum.GetStringValue(enumMsg), sText));                
            }

I hope this will work.