Process.GetProcessById claims killed process is still alive in .NET Core

[bouchraRekhadda]

Description

Process.GetProcessById should throw an ArgumentException if the process isn't running, but it doesn't seem to be the case with .NET Core 3.1 as the method always returns previously killed process (please check repro below).
Am I missing something ?

Reproduction Steps

        [Test] public void TestKillProcess()
        {
            var p = new Process();
            p.StartInfo.FileName = "cmd.exe";
            p.Start();
            var pid = p.Id;
            p.Kill();
            Assert.Throws<ArgumentException>(() => Process.GetProcessById(pid));
        }

Expected behavior

Test should pass as in .NET Framework 4.8

Actual behavior

Test fails

Regression?

It works on .NET Framework 4.8.

Configuration

• .NET Core 3.1
• Windows 10
• x64

Other information

No response

Tagging subscribers to this area: @dotnet/area-system-diagnostics-process
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Process.GetProcessById should throw an ArgumentException if the process isn't running, but it doesn't seem to be the case with .NET Core 3.1 as the method always returns previously killed process (please check repro below).
Am I missing something ?

Reproduction Steps

        [Test] public void TestKillProcess()
        {
            var p = new Process();
            p.StartInfo.FileName = "cmd.exe";
            p.Start();
            var pid = p.Id;
            p.Kill();
            Assert.Throws<ArgumentException>(() => Process.GetProcessById(pid));
        }

Expected behavior

Test should pass as in .NET Framework 4.8

Actual behavior

Test fails

Regression?

It works on .NET Framework 4.8

Known Workarounds

I am not aware of any, our way to check if a process is alive or not is through

       private static bool ProcessIsAlive(int id)
        {
            try
            {
                using (Process.GetProcessById(id))
                    return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

Configuration

• .NET Core 3.1
• Windows 10
• x64
• Doesn't apply
• Doesn't apply

Other information

No response

Author:	bouchraRekhadda
Assignees:	-
Labels:	area-System.Diagnostics.Process, untriaged
Milestone:	-

[KalleOlaviNiemitalo]

This was also reported in #20725 (comment) and PowerShell/PowerShell#12880. Both of those issues have been closed but AFAIK the bug still hasn't been fixed. You can work around the bug by checking Process.HasExited.

[stephentoub]

Yeah, the ProcessManager.IsProcessRunning method should really be running the same logic that UpdateHasExited uses. That logic can probably just be factored out into a helper used by both IsProcessRunning and UpdateHasExited.