How to check if process is still running before calling Process.GetProcessById?

Question

In .NET Process.GetProcessById throws an exception if the process with this ID is not running. How to safely call this method so that it won't throw an exception? I am thinking something like

if(Process.IsRunning(id)) return Process.GetProcessById(id);
else return null; //or do something else

But can't find any method to check the ID, other than probably getting all the running processes and check whether the id exist in the list.

In my experience and testing, the performance of coding by exception like that is very bad — Louis Rhys, Feb 20 '13 at 09:02
So it is about performance?? Well, if you just surround these two lines with try-catch it wouldn't hurt, I believe... — bash.d, Feb 20 '13 at 09:03

score 17 · Accepted Answer · edited Jan 15 '15 at 12:25

public Process GetProcByID(int id)
{
    Process[] processlist = Process.GetProcesses();
    return processlist.FirstOrDefault(pr => pr.Id == id);
}

I looked inside Process.GetProcessById method.

It uses internal static class ProcessManager to ensure, that process runs. ProcessManager gets all the processes currently running in system and checks there ids, so I think it is the best way to do it.

So you should consider the overhead of exception or the overhead of Process array.

score 3 · Answer 2 · answered Feb 20 '13 at 09:00

3

Just use try-catch block

Process p = null;
try{
  p = Process.GetProcessById(id);
}
catch(Exception){

}
return p;

answered Feb 20 '13 at 09:00

Blablablaster

3,238
3
31
33

score 1 · Answer 3 · answered Feb 20 '13 at 09:06

1

Yeah, using try + catch will probably do the trick. If the process is not running, nothing will happen instead of throwing an exception.

answered Feb 20 '13 at 09:06

Mārtiņš Radiņš

365
4
15

score 1 · Answer 4 · answered Feb 16 '19 at 21:21

Same code using pinvoke, this should be faster as GetProcesses, as it does not require all processes enumeration.

[DllImport("kernel32.dll", SetLastError = true)]
public static extern IntPtr OpenProcess(ProcessAccessFlags access, bool inheritHandle, int procId);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CloseHandle(IntPtr hObject);

[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetExitCodeProcess(IntPtr hProcess, out uint lpExitCode);

[Flags]
public enum ProcessAccessFlags : uint
{
    All = 0x001F0FFF,
    Terminate = 0x00000001,
    CreateThread = 0x00000002,
    VirtualMemoryOperation = 0x00000008,
    VirtualMemoryRead = 0x00000010,
    VirtualMemoryWrite = 0x00000020,
    DuplicateHandle = 0x00000040,
    CreateProcess = 0x000000080,
    SetQuota = 0x00000100,
    SetInformation = 0x00000200,
    QueryInformation = 0x00000400,
    QueryLimitedInformation = 0x00001000,
    Synchronize = 0x00100000
}


/// <summary>
/// Checks if given process is still alive
/// </summary>
/// <param name="processId">process id</param>
/// <returns>true if process is alive, false if not</returns>
static public bool IsProcessAlive(int processId)
{
    IntPtr h = OpenProcess(ProcessAccessFlags.QueryInformation, true, processId);

    if (h == IntPtr.Zero)
        return false;

    uint code = 0;
    bool b = GetExitCodeProcess(h, out code);
    CloseHandle(h);

    if (b)
        b = (code == 259) /* STILL_ACTIVE  */;

    return b;
}

How to check if process is still running before calling Process.GetProcessById?

4 Answers4