using System;

using OpenQA.Selenium;

using OpenQA.Selenium.Chrome;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        ChromeDriver driver = new ChromeDriver();

        string page_to_screenshot = "https://google.com";

        driver.Url = page_to_screenshot;

        //Dictionary will contain the parameters needed to get the full page screen shot

        Dictionary<string, Object> metrics = new Dictionary<string, Object>(); 

        metrics["width"] = driver.ExecuteScript("return Math.max(window.innerWidth,document.body.scrollWidth,document.documentElement.scrollWidth)");

        metrics["height"] = driver.ExecuteScript("return Math.max(window.innerHeight,document.body.scrollHeight,document.documentElement.scrollHeight)");

        metrics["deviceScaleFactor"] = (double)driver.ExecuteScript("return window.devicePixelRatio");

        metrics["mobile"] = driver.ExecuteScript("return typeof window.orientation !== 'undefined'");

        //Execute the emulation Chrome Command to change browser to a custom device that is the size of the entire page

        driver.ExecuteChromeCommand("Emulation.setDeviceMetricsOverride", metrics);

        //You can then just screenshot it as it thinks everything is visible

        string path_to_save_screenshot = @"C:/temp/temp.png";

        driver.GetScreenshot().SaveAsFile(path_to_save_screenshot, ScreenshotImageFormat.Png);

        //This command will return your browser back to a normal, usable form if you need to do anything else with it.

        driver.ExecuteChromeCommand("Emulation.clearDeviceMetricsOverride", new Dictionary<string, Object>());

        driver.Close();

    }

}