Process.Id Property

Definition

Namespace:

System.Diagnostics

Assembly:

System.Diagnostics.Process.dll

Source:

Process.cs

Gets the unique identifier for the associated process.

public:
 property int Id { int get(); };

public int Id { get; }

member this.Id : int

Public ReadOnly Property Id As Integer

Property Value

Int32

The system-generated unique identifier of the process that is referenced by this Process instance.

Exceptions

InvalidOperationException

The process's Id property has not been set.

-or-

There is no process associated with this Process object.

Examples

The following example demonstrates how to obtain the Id for all running instances of an application. The code creates a new instance of Notepad, lists all the instances of Notepad, and then allows the user to enter the Id number to remove a specific instance.

using System;
using System.Threading;
using System.Security.Permissions;
using System.Security.Principal;
using System.Diagnostics;

class ProcessDemo
{
    public static void Main()
    {
        Process notePad = Process.Start("notepad");
        Console.WriteLine("Started notepad process Id = " + notePad.Id);
        Console.WriteLine("All instances of notepad:");
        // Get Process objects for all running instances on notepad.
        Process[] localByName = Process.GetProcessesByName("notepad");
        int i = localByName.Length;
        while (i > 0)
        {
            // You can use the process Id to pass to other applications or to
            // reference that particular instance of the application.
            Console.WriteLine(localByName[i - 1].Id.ToString());
            i -= 1;
        }

        i = localByName.Length;
        while (i > 0)
        {
            Console.WriteLine("Enter a process Id to kill the process");
            string id = Console.ReadLine();
            if (string.IsNullOrEmpty(id))
                break;

            try
            {
                using (Process chosen = Process.GetProcessById(Int32.Parse(id)))
                {
                    if (chosen.ProcessName == "notepad")
                    {
                        chosen.Kill();
                        chosen.WaitForExit();
                    }
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("Incorrect entry.");
                continue;
            }

            i -= 1;
        }
    }
}

open System
open System.Diagnostics

let notePad = Process.Start "notepad"
printfn $"Started notepad process Id = {notePad.Id}"
printfn "All instances of notepad:"
// Get Process objects for all running instances on notepad.
let localByName = Process.GetProcessesByName "notepad"
let mutable i = localByName.Length

while i > 0 do
    // You can use the process Id to pass to other applications or to
    // reference that particular instance of the application.
    printfn $"{localByName.[i - 1].Id}"
    i <- i - 1

i <- localByName.Length

while i > 0 do
    printfn "Enter a process Id to kill the process"
    let id = Console.ReadLine()

    if String.IsNullOrEmpty id then
        i <- 0
    else
        try
            use chosen = Int32.Parse id |> Process.GetProcessById

            if chosen.ProcessName = "notepad" then
                chosen.Kill()
                chosen.WaitForExit()

            i <- i - 1
        with e ->
            printfn "Incorrect entry."

Imports System.Threading
Imports System.Security.Permissions
Imports System.Security.Principal
Imports System.Diagnostics



Class ProcessDemo

    Public Shared Sub Main()
        Dim notePad As Process = Process.Start("notepad")
        Console.WriteLine("Started notepad process Id = " + notePad.Id.ToString())
        Console.WriteLine("All instances of notepad:")
        ' Get Process objects for all running instances on notepad.
        Dim localByName As Process() = Process.GetProcessesByName("notepad")
        Dim i As Integer = localByName.Length
        While i > 0
            ' You can use the process Id to pass to other applications or to
            ' reference that particular instance of the application.
            Console.WriteLine(localByName((i - 1)).Id.ToString())
            i -= 1
        End While

        i = localByName.Length
        While i > 0
            Console.WriteLine("Enter a process Id to kill the process")
            Dim id As String = Console.ReadLine()
            If id = String.Empty Then
                Exit While
            End If
            Try
                Using chosen As Process = Process.GetProcessById(Int32.Parse(id))
                    If chosen.ProcessName = "notepad" Then
                        chosen.Kill()
                        chosen.WaitForExit()
                    End If
                End Using
            Catch e As Exception
                Console.WriteLine("Incorrect entry.")
                GoTo ContinueWhile1
            End Try
            i -= 1
ContinueWhile1:
        End While

    End Sub
End Class

Remarks

The process Id is not valid if the associated process is not running. Therefore, you should ensure that the process is running before attempting to retrieve the Id property. Until the process terminates, the process identifier uniquely identifies the process throughout the system.

You can connect a process that is running on a local or remote computer to a new Process instance by passing the process identifier to the GetProcessById method. GetProcessById is a static method that creates a new component and sets the Id property for the new Process instance automatically.

Process identifiers can be reused by the system. The Id property value is unique only while the associated process is running. After the process has terminated, the system can reuse the Id property value for an unrelated process.

Because the identifier is unique on the system, you can pass it to other threads as an alternative to passing a Process instance. This action can save system resources yet guarantee that the process is correctly identified.

See also

• Handle
• GetProcessById(Int32, String)