Paste Line to Notepad for a file, if it is opened by user

Question

i am creating a logging mechanism for my program , where i have to log data in to a file, whose location and name is specified by users.

I am doing the logging using stream writer as follows-

 StreamWriter writer = Writer ?? File.AppendText(FileName);

                writer.WriteLine(DateTime.Now + " " + text);
                writer.Flush();
                writer.Close();

But if user opens the file while my program is running , the newly logged lines are not visible to user until the user close and reopens the file, Is their any way i can overcome this behavior and user is also able to see the newly logged lines when file is open.

ankush · Accepted Answer · 2013-09-02T03:00:41.580

Found a solution using FindWindow and sendmessage following is the code for same-

 [DllImport("user32.dll", EntryPoint = "FindWindow")]
        private static extern IntPtr FindWindow(string lp1, string lp2);
        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        extern static IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, [In] string lpClassName, [In] string lpWindowName);

        [DllImport("User32.dll", EntryPoint = "SendMessage")]
        extern static int SendMessageGetTextLength(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);

        [DllImport("User32.dll")]
        public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);

        [DllImport("User32.dll")]
        public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, int lParam);

  // Writes text line into log file. 
        // If the log file is opened with notepad, it is pasted there instead
        static public void Log(string inputText, DateTime startTime = new DateTime())
        {

            try 
            {

           /*     DateTime now = DateTime.Now;
                inputText = now.ToString() + " " + inputText;
                if (startTime != new DateTime())
                {
                    double diffTime = (int)(now - startTime).TotalMilliseconds;
                    String t;
                    if (diffTime >= 10000)
                        t = ((int) diffTime / 10000).ToString() + " s";
                    else
                        t = ((int)diffTime).ToString() + " ms";

                    inputText += ", " + t;
                }
*/ //irrelevant to the answer

                // search for log file opened with notepad
                IntPtr editBox = GetNotepadWindow();
                if (editBox == IntPtr.Zero)
                {
                    // log file is not open => append line to file
                    try
                    {
                        var writer = new StreamWriter(LogFile, true);
                        writer.WriteLine(inputText);
                        writer.Flush();
                        writer.Close();
                    }
                    catch
                    {
                    }
                    return;
                }
                // paste line into notepad
                int length = SendMessageGetTextLength(editBox, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero);                 
                SendMessage(editBox, EM_SETSEL, length, length);    // search end of file position

                inputText += "\r\n";
                SendMessage(editBox, EM_REPLACESEL, 1, inputText);  // append new line
            }
            catch
            {
            }
        }

        static private IntPtr GetNotepadWindow()
        {
            string windowName = LogFile;
            if (string.IsNullOrEmpty(LogFile))
                windowName = "Untitled";

            int index = windowName.LastIndexOf('\\');
            if (index >= 0)
                windowName = windowName.Substring(index+1);

            IntPtr mainWindow = FindWindow("Notepad", windowName + " - Notepad");
            IntPtr editBox = IntPtr.Zero;

            if (mainWindow != IntPtr.Zero)
                editBox = FindWindowEx(mainWindow, new IntPtr(0), "Edit", null);

            return editBox;
        }

Paste Line to Notepad for a file, if it is opened by user

1 Answers1