https://github.com/npocmaka/batch.scripts/blob/master/hybrids/.net/c/screenCapture.bat

This script will make an exe that can take a screenshot of the screen using command line

// 2>nul||@goto :batch
/*
:batch
@echo off
setlocal

:: find csc.exe
set “csc=”
for /r “%SystemRoot%\Microsoft.NET\Framework\” %%# in (“*csc.exe”) do set “csc=%%#”

if not exist “%csc%” (
echo no .net framework installed
exit /b 10
)

if not exist “%~n0.exe” (
call %csc% /nologo /r:”Microsoft.VisualBasic.dll” /out:”%~n0.exe” “%~dpsfnx0” || (
exit /b %errorlevel%
)
)
%~n0.exe %*
endlocal & exit /b %errorlevel%

*/

// reference
// https://gallery.technet.microsoft.com/scriptcenter/eeff544a-f690-4f6b-a586-11eea6fc5eb8

using System;
using System.Runtime.InteropServices;
using System.Drawing;
using System.Drawing.Imaging;
using System.Collections.Generic;
using Microsoft.VisualBasic;

/// Provides functions to capture the entire screen, or a particular window, and save it to a file.

public class ScreenCapture
{

/// Creates an Image object containing a screen shot the active window 

public Image CaptureActiveWindow()
{
    return CaptureWindow(User32.GetForegroundWindow());
}

/// Creates an Image object containing a screen shot of the entire desktop 

public Image CaptureScreen()
{
    return CaptureWindow(User32.GetDesktopWindow());
}

/// Creates an Image object containing a screen shot of a specific window 

private Image CaptureWindow(IntPtr handle)
{
    // get te hDC of the target window 
    IntPtr hdcSrc = User32.GetWindowDC(handle);
    // get the size 
    User32.RECT windowRect = new User32.RECT();
    User32.GetWindowRect(handle, ref windowRect);
    int width = windowRect.right - windowRect.left;
    int height = windowRect.bottom - windowRect.top;
    // create a device context we can copy to 
    IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
    // create a bitmap we can copy it to, 
    // using GetDeviceCaps to get the width/height 
    IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
    // select the bitmap object 
    IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
    // bitblt over 
    GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);
    // restore selection 
    GDI32.SelectObject(hdcDest, hOld);
    // clean up 
    GDI32.DeleteDC(hdcDest);
    User32.ReleaseDC(handle, hdcSrc);
    // get a .NET image object for it 
    Image img = Image.FromHbitmap(hBitmap);
    // free up the Bitmap object 
    GDI32.DeleteObject(hBitmap);
    return img;
}

public void CaptureActiveWindowToFile(string filename, ImageFormat format)
{
    Image img = CaptureActiveWindow();
    img.Save(filename, format);
}

public void CaptureScreenToFile(string filename, ImageFormat format)
{
    Image img = CaptureScreen();
    img.Save(filename, format);
}

static bool fullscreen = true;
static String file = "screenshot.bmp";
static System.Drawing.Imaging.ImageFormat format = System.Drawing.Imaging.ImageFormat.Bmp;
static String windowTitle = "";

static void parseArguments()
{
    String[] arguments = Environment.GetCommandLineArgs();
    if (arguments.Length == 1)
    {
        printHelp();
        Environment.Exit(0);
    }
    if (arguments[1].ToLower().Equals("/h") || arguments[1].ToLower().Equals("/help"))
    {
        printHelp();
        Environment.Exit(0);
    }

    file = arguments[1];
    Dictionary<String, System.Drawing.Imaging.ImageFormat> formats =
    new Dictionary<String, System.Drawing.Imaging.ImageFormat>();

    formats.Add("bmp", System.Drawing.Imaging.ImageFormat.Bmp);
    formats.Add("emf", System.Drawing.Imaging.ImageFormat.Emf);
    formats.Add("exif", System.Drawing.Imaging.ImageFormat.Exif);
    formats.Add("jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
    formats.Add("jpeg", System.Drawing.Imaging.ImageFormat.Jpeg);
    formats.Add("gif", System.Drawing.Imaging.ImageFormat.Gif);
    formats.Add("png", System.Drawing.Imaging.ImageFormat.Png);
    formats.Add("tiff", System.Drawing.Imaging.ImageFormat.Tiff);
    formats.Add("wmf", System.Drawing.Imaging.ImageFormat.Wmf);


    String ext = "";
    if (file.LastIndexOf('.') > -1)
    {
        ext = file.ToLower().Substring(file.LastIndexOf('.') + 1, file.Length - file.LastIndexOf('.') - 1);
    }
    else
    {
        Console.WriteLine("Invalid file name - no extension");
        Environment.Exit(7);
    }

    try
    {
        format = formats[ext];
    }
    catch (Exception e)
    {
        Console.WriteLine("Probably wrong file format:" + ext);
        Console.WriteLine(e.ToString());
        Environment.Exit(8);
    }


    if (arguments.Length > 2)
    {
        windowTitle = arguments[2];
        fullscreen = false;
    }

}

static void printHelp()
{
    //clears the extension from the script name
    String scriptName = Environment.GetCommandLineArgs()[0];
    scriptName = scriptName.Substring(0, scriptName.Length);
    Console.WriteLine(scriptName + " captures the screen or the active window and saves it to a file.");
    Console.WriteLine("");
    Console.WriteLine("Usage:");
    Console.WriteLine(" " + scriptName + " filename  [WindowTitle]");
    Console.WriteLine("");
    Console.WriteLine("filename - the file where the screen capture will be saved");
    Console.WriteLine("     allowed file extensions are - Bmp,Emf,Exif,Gif,Icon,Jpeg,Png,Tiff,Wmf.");
    Console.WriteLine("WindowTitle - instead of capture whole screen you can point to a window ");
    Console.WriteLine("     with a title which will put on focus and captuted.");
    Console.WriteLine("     For WindowTitle you can pass only the first few characters.");
    Console.WriteLine("     If don't want to change the current active window pass only \"\"");
}

public static void Main()
{
    User32.SetProcessDPIAware();

    parseArguments();
    ScreenCapture sc = new ScreenCapture();
    if (!fullscreen && !windowTitle.Equals(""))
    {
        try
        {

            Interaction.AppActivate(windowTitle);
            Console.WriteLine("setting " + windowTitle + " on focus");
        }
        catch (Exception e)
        {
            Console.WriteLine("Probably there's no window like " + windowTitle);
            Console.WriteLine(e.ToString());
            Environment.Exit(9);
        }


    }
    try
    {
        if (fullscreen)
        {
            Console.WriteLine("Taking a capture of the whole screen to " + file);
            sc.CaptureScreenToFile(file, format);
        }
        else
        {
            Console.WriteLine("Taking a capture of the active window to " + file);
            sc.CaptureActiveWindowToFile(file, format);
        }
    }
    catch (Exception e)
    {
        Console.WriteLine("Check if file path is valid " + file);
        Console.WriteLine(e.ToString());
    }
}

/// Helper class containing Gdi32 API functions 

private class GDI32
{

    public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter 
    [DllImport("gdi32.dll")]
    public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
      int nWidth, int nHeight, IntPtr hObjectSource,
      int nXSrc, int nYSrc, int dwRop);
    [DllImport("gdi32.dll")]
    public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
      int nHeight);
    [DllImport("gdi32.dll")]
    public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
    [DllImport("gdi32.dll")]
    public static extern bool DeleteDC(IntPtr hDC);
    [DllImport("gdi32.dll")]
    public static extern bool DeleteObject(IntPtr hObject);
    [DllImport("gdi32.dll")]
    public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
}


/// Helper class containing User32 API functions 

private class User32
{
    [StructLayout(LayoutKind.Sequential)]
    public struct RECT
    {
        public int left;
        public int top;
        public int right;
        public int bottom;
    }
    [DllImport("user32.dll")]
    public static extern IntPtr GetDesktopWindow();
    [DllImport("user32.dll")]
    public static extern IntPtr GetWindowDC(IntPtr hWnd);
    [DllImport("user32.dll")]
    public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
    [DllImport("user32.dll")]
    public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
    [DllImport("user32.dll")]
    public static extern IntPtr GetForegroundWindow();
    [DllImport("user32.dll")]
    public static extern int SetProcessDPIAware();
}

}