Try this
using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Text;
using System.Diagnostics;
using System.Threading;
using System.Reflection;
using System.IO;
namespace SingleInstance
{
/// <summary>
/// Summary description for SingleApp.
/// </summary>
public class SingleApplication
{
public SingleApplication()
{
}
/// <summary>
/// Imports
/// </summary>
[DllImport("user32.dll")]
private static extern int ShowWindow(IntPtr hWnd, int
nCmdShow);
[DllImport("user32.dll")]
private static extern int SetForegroundWindow(IntPtr
hWnd);
[DllImport("user32.dll")]
private static extern int IsIconic(IntPtr hWnd);
/// <summary>
/// GetCurrentInstanceWindowHandle
/// </summary>
/// <returns></returns>
private static IntPtr GetCurrentInstanceWindowHandle()
{
IntPtr hWnd = IntPtr.Zero;
Process process = Process.GetCurrentProcess();
Process[] processes =
Process.GetProcessesByName(process.ProcessName);
foreach(Process _process in processes)
{
// Get the first instance that is not
this instance, has the
// same process name and was started
from the same file name
// and location. Also check that the
process has a valid
// window handle in this session to
filter out other user's
// processes.
if (_process.Id != process.Id &&
_process.MainModule.FileName
== process.MainModule.FileName &&
_process.MainWindowHandle !=
IntPtr.Zero)
{
hWnd =
_process.MainWindowHandle;
break;
}
}
return hWnd;
}
/// <summary>
/// SwitchToCurrentInstance
/// </summary>
private static void SwitchToCurrentInstance()
{
IntPtr hWnd =
GetCurrentInstanceWindowHandle();
if (hWnd != IntPtr.Zero)
{
// Restore window if minimised. Do not
restore if already in
// normal or maximised window state,
since we don't want to
// change the current state of the
window.
if (IsIconic(hWnd) != 0)
{
ShowWindow(hWnd, SW_RESTORE);
}
// Set foreground window.
SetForegroundWindow(hWnd);
}
}
/// <summary>
/// Execute a form base application if another
instance already running on
/// the system activate previous one
/// </summary>
/// <param name="frmMain">main form</param>
/// <returns>true if no previous instance is
running</returns>
public static bool Run(System.Windows.Forms.Form
frmMain)
{
if(IsAlreadyRunning())
{
//set focus on previously running app
SwitchToCurrentInstance();
return false;
}
Application.Run(frmMain);
return true;
}
/// <summary>
/// for console base application
/// </summary>
/// <returns></returns>
public static bool Run()
{
if(IsAlreadyRunning())
{
return false;
}
return true;
}
/// <summary>
/// check if given exe alread running or not
/// </summary>
/// <returns>returns true if already running</returns>
private static bool IsAlreadyRunning()
{
string strLoc =
Assembly.GetExecutingAssembly().Location;
FileSystemInfo fileInfo = new
FileInfo(strLoc);
string sExeName = fileInfo.Name;
bool bCreatedNew;
mutex = new Mutex(true, "Global\\"+sExeName,
out bCreatedNew);
if (bCreatedNew)
mutex.ReleaseMutex();
return !bCreatedNew;
}
static Mutex mutex;
const int SW_RESTORE = 9;
}
}
IN PROGRAM.CS add line
SingleApplication.Run(new frmMain());
