How to set focus back to form after opening up a process (Notepad)?

I had the same problem, i eventually wound up with programmatically calling alt-tab:

[DllImport("user32.dll")]
static extern bool PostMessage(IntPtr hWnd, UInt32 Msg, int wParam, int lParam);

private void alttab()
{
     uint WM_SYSCOMMAND = 0x0112;
     int SC_PREVWINDOW = 0xF050;            

     PostMessage(Process.GetCurrentProcess().MainWindowHandle, WM_SYSCOMMAND, SC_PREVWINDOW, 0);
}

//EDIT: You should use process.MainWindowHandle instead ofcourse

I tried almost everything on internet (so sure about it :)). At best I could get my form on top of all other forms, but without focus (going by @Hans Passant's method). Going by heavy blocks of codes all over, I somehow felt this aint gonna be easy. So I always used SetForegroundWindow() with chunks of other code. Never thought merely SetForegroundWindow() would do the trick.

This worked.

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool SetForegroundWindow(IntPtr hWnd);

private void button1_Click(object sender, EventArgs e)
{ 
    Process process = new Process();
    process.StartInfo.FileName = @...\abc.log";
    process.Start();

    process.WaitForInputIdle(); //this is the key!!

    SetForegroundWindow(this.Handle);
}

At times this method yields in a focus on the parent form (in cases where my desired form is a modal child form of its parent form); in such cases, just add this.Focus() to the last line..

Even this worked:

Microsoft.VisualBasic.Interaction.Shell(@"notepad.exe D:\abc.log", 
                                        Microsoft.VisualBasic.AppWinStyle.NormalNoFocus);

Solution provided by here

If you want to start a process and focus back to the form, then start that process with minimized state, like this:

Dim psi As New ProcessStartInfo("notepad")
psi.WindowStyle = ProcessWindowStyle.Minimized
Process.Start(psi)