How to send text to Notepad in C#/Win32?

    [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
    public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
    [DllImport("User32.dll")]
    public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);
    private void button1_Click(object sender, EventArgs e)
    {
        Process [] notepads=Process.GetProcessesByName("notepad");
        if(notepads.Length==0)return;            
        if (notepads[0] != null)
        {
            IntPtr child= FindWindowEx(notepads[0].MainWindowHandle, new IntPtr(0), "Edit", null);
            SendMessage(child, 0x000C, 0, textBox1.Text);
        }
    }

WM_SETTEXT=0x000c

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