Programmatically Switch to Another Running Application/Process

Question
In my Windows application, I want to be able to switch to another application running on my computer. For example, I want to switch to Internet Explorer and make it the active window. How do I do that?

Answer
To solve this problem, you need to first obtain the list of processes currently running on your system. You then need to find the required application/process to switch to and then make that window active.

First, import the following namespace:

using System.Diagnostics;

Then, declare the following functions from the user32.dll (yes, you will use P/Invoke to switch the current active window):

    public partial class Form1 : Form
    {
        [DllImport("user32.dll")]
           private static extern bool
           SetForegroundWindow(IntPtr hWnd);

        [DllImport("user32.dll")]
           private static extern bool ShowWindowAsync(
           IntPtr hWnd, int nCmdShow);

Define the following constant:

        private const int SW_RESTORE = 9;
     
Assuming that you want to switch to IE, the following function will retrieve the list of processes running, look for IE, and then make it the active window:

        private void SwitchToIE()
        {
            Process[] procs = Process.GetProcesses();
            if (procs.Length != 0)
            {
                for (int i = 0; i < procs.Length; i++)
                {
                    try
                    {
                        if (procs[i].MainModule.ModuleName ==
                           "IEXPLORE.EXE")
                        {
                            IntPtr hwnd =
                               procs[i].MainWindowHandle;
                            ShowWindowAsync(hwnd, SW_RESTORE);
                            SetForegroundWindow(hwnd);
                            return;
                        }
                    }
                    catch
                    {
                    }
                }
            }
            else
            {
                MessageBox.Show("No process running");
                return;
            }
            MessageBox.Show(
               "Internet Explorer is not running");
        }

Voila! If at least one instance of IE is running, you will be able to switch to it; else it will display the message “Internet Explorer is not running”.