using NUnit.Framework;
        using OpenQA.Selenium;
        using OpenQA.Selenium.Chrome;
        using OpenQA.Selenium.Firefox;
        using System;
        using System.Collections.Generic;
        using System.Diagnostics;
        using System.Linq;
        using System.Text;
        using System.Threading.Tasks;
        using OpenQA.Selenium.Support.PageObjects;

        namespace ToolsQA
        {

            class NUnitTest
            {
                [FindsBy(How = How.CssSelector, Using = "input[name='q']")][CacheLookup]
                public IWebElement serchBox { get; set; }

                string url = "https://www.google.com";
                IWebDriver driver;
                [Test]
                public void TestScript()
                {
                    driver = new ChromeDriver(@"C:ChromeDriver");
                    driver.Navigate().GoToUrl(url);
                   ////// exception at this line //////
                    serchBox.SendKeys("beyonce");
                }

                [TearDown]
                public void EndTest()
                {
                    driver.Quit();
                }
            }
        }