ChromeDriver does not exist in Selenium WebDriver C# test script
Since you're using C#, you should use the constructor overload for ChromeDriver that allows you to specify the path to the directory containing chromedriver.exe. To wit:
IWebDriver driver = new ChromeDriver(@"C:\my\path\to\chromedriver\directory");
Old question, new answer (for what it's worth): just install the Nuget package Selenium.WebDriver.ChromeDriver. Chromedriver.exe will be in the directory bin/debug on the next build.
3rd party edit 2017-09
On this github page jsakamoto/nupkg-selenium-webdriver-chromedriver/ that after running Install-Package Selenium.WebDriver -Version 3.5.2
the chromedriver(.exe) lies below this folder
" {solution folder} /packages/Selenium.WebDriver.ChromeDriver. {ver} /driver/ {platform}"
Could this be because NuGet packages are being loaded from a global place instead of the packages folder of the .NET Framework projects. This worked for me:
IWebDriver driver = new ChromeDriver(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location));