C#

string userPath = 
    Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
string allUsersPath = 
    Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);

using System;
using System.IO;

namespace ConsoleApplication
{
    class Program
    {
        public static readonly string UserPath = 
            Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
        public static readonly string AllUsersPath = 
            Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);

        static void Main(string[] args)
        {
            try
            {
                string fileName = "Test.txt";
                string textToSave = "AbcDefGhi";

                string userFilePath = Path.Combine(UserPath, fileName);
                string allUsersFilePath = Path.Combine(AllUsersPath, fileName);

                using (TextWriter userTextWriter = new StreamWriter(userFilePath),
                allUsersTextWriter = new StreamWriter(allUsersFilePath))
                {
                    Console.WriteLine("Writing {0} to {1}", textToSave, userFilePath);
                    userTextWriter.WriteLine(textToSave);
                    Console.WriteLine("Writing {0} to {1}", textToSave, allUsersFilePath);
                    allUsersTextWriter.WriteLine(textToSave);
                }

                using (TextReader userTextReader = new StreamReader(userFilePath),
                allUsersTextReader = new StreamReader(allUsersFilePath))
                {
                    Console.WriteLine("Reading from {0}", userFilePath);
                    Console.WriteLine(userTextReader.ReadLine());
                    Console.WriteLine("Reading from {0}", allUsersFilePath);
                    Console.WriteLine(allUsersTextReader.ReadLine());
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
            Console.ReadKey();
        }
    }
}

Problem Event Name:   CLR20r3
Problem Signature 01: consoleapplication.exe
Problem Signature 02: 1.0.0.0
Problem Signature 03: 4b89d18d
Problem Signature 04: mscorlib
Problem Signature 05: 2.0.0.0
Problem Signature 06: 4a275af7
Problem Signature 07: 344b
Problem Signature 08: 15a
Problem Signature 09: System.UnauthorizedAccess
OS Version:   6.1.7600.2.0.0.256.1
Locale ID:    2057

System.UnauthorizedAccessException:
Access to the path 'X:\ProgramData\Test.txt' is denied.

using System;
using System.IO;
using System.Security.AccessControl;

namespace ConsoleApplication
{
    class Program
    {
        public static readonly string UserPath = 
            Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
        public static readonly string AllUsersPath = 
            Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);

        static void Main(string[] args)
        {
            try
            {
                string folderName = "Test";
                string fileName = "Test.txt";
                string textToSave = "AbcDefGhi";

                string userDirectory = Path.Combine(UserPath, folderName);
                string allUsersDirectory = Path.Combine(AllUsersPath, folderName);

                string userFilePath = Path.Combine(userDirectory, fileName);
                string allUsersFilePath = Path.Combine(allUsersDirectory, fileName);

                CreateDirectoryWithPermissions(userDirectory);
                CreateDirectoryWithPermissions(allUsersDirectory);

                using (TextWriter userTextWriter = new StreamWriter(userFilePath),
                allUsersTextWriter = new StreamWriter(allUsersFilePath))
                {
                    Console.WriteLine("Writing {0} to {1}", textToSave, userFilePath);
                    userTextWriter.WriteLine(textToSave);
                    Console.WriteLine("Writing {0} to {1}", textToSave, allUsersFilePath);
                    allUsersTextWriter.WriteLine(textToSave);
                }

                using (TextReader userTextReader = new StreamReader(userFilePath),
                allUsersTextReader = new StreamReader(allUsersFilePath))
                {
                    Console.WriteLine("Reading from {0}", userFilePath);
                    Console.WriteLine(userTextReader.ReadLine());
                    Console.WriteLine("Reading from {0}", allUsersFilePath);
                    Console.WriteLine(allUsersTextReader.ReadLine());
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
            Console.ReadKey();
        }

        private static void CreateDirectoryWithPermissions(string path)
        {
            if (!Directory.Exists(path))
            {
                bool modified = false;
                DirectoryInfo directoryInfo = directoryInfo = Directory.CreateDirectory(path);
                DirectorySecurity directorySecurity = directoryInfo.GetAccessControl();
                AccessRule rule = new FileSystemAccessRule(
                    "Users",
                    FileSystemRights.Write |
                    FileSystemRights.ReadAndExecute |
                    FileSystemRights.Modify,
                    InheritanceFlags.ContainerInherit |
                    InheritanceFlags.ObjectInherit,
                    PropagationFlags.InheritOnly,
                    AccessControlType.Allow);
                directorySecurity.ModifyAccessRule(AccessControlModification.Add, rule, out modified);
                directoryInfo.SetAccessControl(directorySecurity);
            }
        }
    }
}