I have come across a few people with the same issue that seemed to have solved the problem with System.addProperty(\"webdriver.chrome.driver\", \".../chromedriver.exe\");<
I found that although the Selenium.WebDriver.ChromeDriver NuGet package had been downloaded and consequently the chromedriver.exe file was being copied into the bin folder at compile time, additionally it needed to be marked as a deployment item (because it is a unit test that copied-into/run-from the TestResults folder) - i.e.
[DeploymentItem(@"chromedriver.exe")]