c# Перехватываем любое окно в Windows и вводим в него текст или прячем

Передаем какой то текст в окно,как будто вводим с клавиатуры и жмем ОК кнопкой Enter:

int iHandle = Common.NativeWin32.FindWindow(null, "Сюда пишем заголовок нужного окна");
Common.NativeWin32.SetForegroundWindow(iHandle);
System.Windows.Forms.SendKeys.SendWait("Здесь пишем текст который нужно ввести в это окно");
//Жмем в окне Enter   
System.Windows.Forms.SendKeys.SendWait("{ENTER}");

По аналогии прячем окно:

int iHandle = Common.NativeWin32.FindWindow(null, "Заголовок окна");
Common.NativeWin32.SetWindowPos(new IntPtr(iHandle), Common.NativeWin32.HWND.Top, 0, 0, 0, 0, Common.NativeWin32.SetWindowPosFlags.AsynchronousWindowPosition);

Вспомогательный класс:

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace DeclTerminalApp.Common
{
    class NativeWin32
    {
        public const int WM_SYSCOMMAND = 0x0112;
        public const int SC_CLOSE = 0xF060;

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, SetWindowPosFlags uFlags);

        static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);
        static readonly IntPtr HWND_NOTOPMOST = new IntPtr(-2);
        static readonly IntPtr HWND_TOP = new IntPtr(0);
        static readonly IntPtr HWND_BOTTOM = new IntPtr(1);

        /// <summary>
        /// Window handles (HWND) used for hWndInsertAfter
        /// </summary>
        public static class HWND
        {
            public static IntPtr
            NoTopMost = new IntPtr(-2),
            TopMost = new IntPtr(-1),
            Top = new IntPtr(0),
            Bottom = new IntPtr(1);
        }

        /// <summary>
        /// SetWindowPos Flags
        /// </summary>
        public static class SWP
        {
            public static readonly int
            NOSIZE = 0x0001,
            NOMOVE = 0x0002,
            NOZORDER = 0x0004,
            NOREDRAW = 0x0008,
            NOACTIVATE = 0x0010,
            DRAWFRAME = 0x0020,
            FRAMECHANGED = 0x0020,
            SHOWWINDOW = 0x0040,
            HIDEWINDOW = 0x0080,
            NOCOPYBITS = 0x0100,
            NOOWNERZORDER = 0x0200,
            NOREPOSITION = 0x0200,
            NOSENDCHANGING = 0x0400,
            DEFERERASE = 0x2000,
            ASYNCWINDOWPOS = 0x4000;
        }

        [Flags()]
        public enum SetWindowPosFlags : uint
        {
            /// <summary>If the calling thread and the thread that owns the window are attached to different input queues, 
            /// the system posts the request to the thread that owns the window. This prevents the calling thread from 
            /// blocking its execution while other threads process the request.</summary>
            /// <remarks>SWP_ASYNCWINDOWPOS</remarks>
            AsynchronousWindowPosition = 0x4000,
            /// <summary>Prevents generation of the WM_SYNCPAINT message.</summary>
            /// <remarks>SWP_DEFERERASE</remarks>
            DeferErase = 0x2000,
            /// <summary>Draws a frame (defined in the window's class description) around the window.</summary>
            /// <remarks>SWP_DRAWFRAME</remarks>
            DrawFrame = 0x0020,
            /// <summary>Applies new frame styles set using the SetWindowLong function. Sends a WM_NCCALCSIZE message to 
            /// the window, even if the window's size is not being changed. If this flag is not specified, WM_NCCALCSIZE 
            /// is sent only when the window's size is being changed.</summary>
            /// <remarks>SWP_FRAMECHANGED</remarks>
            FrameChanged = 0x0020,
            /// <summary>Hides the window.</summary>
            /// <remarks>SWP_HIDEWINDOW</remarks>
            HideWindow = 0x0080,
            /// <summary>Does not activate the window. If this flag is not set, the window is activated and moved to the 
            /// top of either the topmost or non-topmost group (depending on the setting of the hWndInsertAfter 
            /// parameter).</summary>
            /// <remarks>SWP_NOACTIVATE</remarks>
            DoNotActivate = 0x0010,
            /// <summary>Discards the entire contents of the client area. If this flag is not specified, the valid 
            /// contents of the client area are saved and copied back into the client area after the window is sized or 
            /// repositioned.</summary>
            /// <remarks>SWP_NOCOPYBITS</remarks>
            DoNotCopyBits = 0x0100,
            /// <summary>Retains the current position (ignores X and Y parameters).</summary>
            /// <remarks>SWP_NOMOVE</remarks>
            IgnoreMove = 0x0002,
            /// <summary>Does not change the owner window's position in the Z order.</summary>
            /// <remarks>SWP_NOOWNERZORDER</remarks>
            DoNotChangeOwnerZOrder = 0x0200,
            /// <summary>Does not redraw changes. If this flag is set, no repainting of any kind occurs. This applies to 
            /// the client area, the nonclient area (including the title bar and scroll bars), and any part of the parent 
            /// window uncovered as a result of the window being moved. When this flag is set, the application must 
            /// explicitly invalidate or redraw any parts of the window and parent window that need redrawing.</summary>
            /// <remarks>SWP_NOREDRAW</remarks>
            DoNotRedraw = 0x0008,
            /// <summary>Same as the SWP_NOOWNERZORDER flag.</summary>
            /// <remarks>SWP_NOREPOSITION</remarks>
            DoNotReposition = 0x0200,
            /// <summary>Prevents the window from receiving the WM_WINDOWPOSCHANGING message.</summary>
            /// <remarks>SWP_NOSENDCHANGING</remarks>
            DoNotSendChangingEvent = 0x0400,
            /// <summary>Retains the current size (ignores the cx and cy parameters).</summary>
            /// <remarks>SWP_NOSIZE</remarks>
            IgnoreResize = 0x0001,
            /// <summary>Retains the current Z order (ignores the hWndInsertAfter parameter).</summary>
            /// <remarks>SWP_NOZORDER</remarks>
            IgnoreZOrder = 0x0004,
            /// <summary>Displays the window.</summary>
            /// <remarks>SWP_SHOWWINDOW</remarks>
            ShowWindow = 0x0040,
        }

        [DllImport("user32.dll")]
        public static extern int FindWindow(
            string lpClassName, // class name 
            string lpWindowName // window name 
        );

        [DllImport("user32.dll")]
        public static extern int SendMessage(
            int hWnd, // handle to destination window 
            uint Msg, // message 
            int wParam, // first message parameter 
            int lParam // second message parameter 
        );

        [DllImport("user32.dll")]
        public static extern int SetForegroundWindow(
            int hWnd // handle to window
            );

        private const int GWL_EXSTYLE = (-20);
        private const int WS_EX_TOOLWINDOW = 0x80;
        private const int WS_EX_APPWINDOW = 0x40000;
              
        public const int GW_HWNDFIRST = 0;
        public const int GW_HWNDLAST  = 1;
        public const int GW_HWNDNEXT  = 2;
        public const int GW_HWNDPREV  = 3;
        public const int GW_OWNER     = 4;
        public const int GW_CHILD     = 5;

        public delegate int EnumWindowsProcDelegate(int hWnd, int lParam);

        [DllImport("user32")]
        public static extern int EnumWindows(EnumWindowsProcDelegate lpEnumFunc, int lParam);

        [DllImport("User32.Dll")]
        public static extern void GetWindowText(int h, StringBuilder s, int nMaxCount);

        [DllImport("user32", EntryPoint = "GetWindowLongA")]
        public static extern int GetWindowLongPtr(int hwnd, int nIndex);

        [DllImport("user32")]
        public static extern int GetParent(int hwnd);

        [DllImport("user32")]
        public static extern int GetWindow(int hwnd, int wCmd);

        [DllImport("user32")]
        public static extern int IsWindowVisible(int hwnd);

        [DllImport("user32")]
        public static extern int GetDesktopWindow();
    }
}