Lab_4/15var (IV semester) OS&SP

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Lab4
{
    public partial class Lab_4 : Form
    {
        public static Lab_4 Instance { get; private set; }

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr FindWindow(string className, string windowName);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern int SendMessage(IntPtr hwnd, int wMessage, int wParam, int lParam);
        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        private static extern uint RegisterWindowMessage(string lpString);

        private uint messageId = RegisterWindowMessage("777");

        public Lab_4(){
            if (Instance == null)
                Instance = this;
            InitializeComponent();

        }
        protected override void WndProc(ref Message m) {
            if (m.Msg == messageId)
                chatHistory.AppendText(((char)m.WParam).ToString());
            base.WndProc(ref m);
        }
        private void SendButton_Click(object sender, EventArgs e)
        {
            if (!(string.IsNullOrEmpty(message.Text) ||
                string.IsNullOrEmpty(to.Text) ||
                string.IsNullOrEmpty(username.Text)))
            {
                string result = "Message from " + username.Text + " in " + DateTime.Now.ToShortTimeString() + ": " + message.Text + "\r\n";
                IntPtr windowToFind = FindWindow(null, to.Text);
                for (int i = 0; i < result.Length; i++)
                    SendMessage(windowToFind, (int)messageId, result[i], 0);
                chatHistory.AppendText(result);
                message.Text = "";
            }
        }
        private void nameText_TextChanged(object sender, EventArgs e) {
            Text = Name = username.Text;
        }

        private void messageText_KeyPress(object sender, KeyPressEventArgs e){
            if (e.KeyChar == (char)Keys.Enter){
                send.PerformClick();
            }
        }
    }
}