How does FileIOPermissions work in conjunction with IIS?  What level is responsible for allowing file output/writing for web applications (i.e. IIS or Integrated Windows Authentication ...)

Greetings:

I have plenty of .Net applications that do not require any sort of FileIOPermissions to write out a log file.  I'm new to Web development and I'm finding the same rule is not true when trying to write out a log file for debugging purposes.

Please look at the code snippet I use for non Web applications.  If I try to call this code from my web application I get the following error:

System.UnauthorizedAccessException was unhandled by user code
  Message="Access to the path 'C:\\ApplicationLog.txt' is denied."
  Source="mscorlib"
  StackTrace:
       at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
       at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
       at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy)
       at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
       at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize)
       at System.IO.StreamWriter..ctor(String path, Boolean append)
       at WriteToFile.FileWriter.WriteToFile(String FileDest, String StrOutput) in C:\Projects\WriteToFile\WriteToFile.cs:line 25


Do I need to incorportate FileIOPermissions to get this to work or do I need to modify IIS permissions, Windows permisssions, drive permissions???  I tried adding the 'write' permission to the site directory but I don't think this is not the answer if I want to write to the 'C' drive.

Where is this error coming from?

Thanks!



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using System;
using System.IO;
 
namespace WriteToFile
{
    public class FileWriter
    {
        // Set this to false to stop writing to file
        private static bool _WriteToFile = true;
 
        public void WriteToFile(string FileDest, string StrOutput)
        {
             if (_WriteToFile)
            {
 
                // create a writer and open the file
                TextWriter tw = new StreamWriter(FileDest, true);
 
                // write a line of text to the file
                tw.WriteLine(StrOutput);
 
                // close the stream
                tw.Close();
            }
        }
    }
}