PingTool/Program.cs

using System;
using System.Diagnostics;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Threading;

namespace PingTool
{
    static class Program
    {
        private const int WH_KEYBOARD_LL = 13;
        private const int WM_KEYDOWN = 0x0100;
        private static LowLevelKeyboardProc _proc = HookCallback;
        private static IntPtr _hookID = IntPtr.Zero;
        private static PingToolForm pingToolForm;

        [STAThread]
        public static void Main()
        {
            _hookID = SetHook(_proc);
            bool createdNew;
            using (Mutex mutex = new Mutex(true, "PingTool", out createdNew))
            {
                if (createdNew)
                {
                    Application.EnableVisualStyles();
                    Application.SetCompatibleTextRenderingDefault(false);
                    pingToolForm = new PingToolForm();
                    Application.Run(pingToolForm);
                }
                else
                {
                    Process current = Process.GetCurrentProcess();
                    foreach (Process process in Process.GetProcessesByName(current.ProcessName))
                    {
                        if (process.Id != current.Id)
                        {
                            MessageBox.Show("PingTool: Ứng dụng đã chạy");
                            break;
                        }
                    }
                }
            }
            UnhookWindowsHookEx(_hookID);
        }

        private static IntPtr SetHook(LowLevelKeyboardProc proc)
        {
            using (Process curProcess = Process.GetCurrentProcess())
            using (ProcessModule curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0);
            }
        }

        private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

        private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
            {
                int vkCode = Marshal.ReadInt32(lParam);
                if (Keys.Control == Control.ModifierKeys && Keys.F11 == (Keys)vkCode)
                {
                    pingToolForm.Show();
                    pingToolForm.ShowInTaskbar = true;
                    pingToolForm.WindowState = FormWindowState.Normal;
                }

                if (Keys.Control == Control.ModifierKeys && Keys.F9 == (Keys)vkCode)
                {
                    if (pingToolForm.ShowInTaskbar == true)
                    {
                        pingToolForm.Hide();
                        pingToolForm.ShowInTaskbar = false;
                        pingToolForm.WindowState = FormWindowState.Minimized;
                    }
                }
            }

            return CallNextHookEx(_hookID, nCode, wParam, lParam);
        }

        [DllImport(Constant.USER_32_DLL, CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

        [DllImport(Constant.USER_32_DLL, CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);

        [DllImport(Constant.USER_32_DLL, CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport(Constant.KERNEL_32_DLL, CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);
    }
}