.net console application execute as differnet user :
or
.net  read file as a different user etc :

 using (UserImpersonation user = new UserImpersonation(uname, Domain, pass))
            {
                if (user.ImpersonateValidUser())
                {

                    //write your code to read file or access items etc ..
                 }
}

wehn you run the code you can see if you are successful to login as that user or not .if you are logged it it show old user and impersonating user details .


right click on UserImpersonation: and select generate a class :

ADD THIS CODE TO THAT GENERATED CLASS FILE :

make sure you add inherit from idisposable .


class UserImpersonation:IDisposable
    {

        [DllImport("advapi32.dll")]
        public static extern bool LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        public static extern bool CloseHandle(IntPtr handle);

        WindowsImpersonationContext wic;
        IntPtr tokenHandle;
        string _userName;
        string _domain;
        string _passWord;

        public UserImpersonation(string userName, string domain, string passWord)
        {
            _userName = userName;
            _domain = domain;
            _passWord = passWord;
        }

        const int LOGON32_PROVIDER_DEFAULT = 0;
        const int LOGON32_LOGON_INTERACTIVE = 2;

        public bool ImpersonateValidUser()
        {
            bool returnValue = LogonUser(_userName, _domain, _passWord,
                    LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
                    ref tokenHandle);

            Console.WriteLine("LogonUser called.");

            if (false == returnValue)
            {
                int ret = Marshal.GetLastWin32Error();
                Console.WriteLine("LogonUser failed with error code : {0}", ret);
                return false;
            }

            Console.WriteLine("Did LogonUser Succeed? " + (returnValue ? "Yes" : "No"));
            Console.WriteLine("Value of Windows NT token: " + tokenHandle);

            // Check the identity.
            Console.WriteLine("Before impersonation: "
                + WindowsIdentity.GetCurrent().Name);
            // Use the token handle returned by LogonUser.
            WindowsIdentity newId = new WindowsIdentity(tokenHandle);
            wic = newId.Impersonate();

            // Check the identity.
            Console.WriteLine("After impersonation: "
                + WindowsIdentity.GetCurrent().Name);
            return true;
        }
     
        public void Dispose()
        {
            if (wic != null)
                wic.Undo();
            if (tokenHandle != IntPtr.Zero)
                CloseHandle(tokenHandle);

        }


    }