new InternetExplorerDriver();

但是我可以看到如下异常：

OpenQA.Selenium.DriverServiceNotFoundException was unhandled by user code
  HResult=-2146233088
  Message=The IEDriverServer.exe file does not exist in the current directory or in a directory on the PATH environment variable. The driver can be downloaded at http://code.google.com/p/selenium/downloads/list.
  Source=WebDriver
  StackTrace:
       at OpenQA.Selenium.DriverService.FindDriverServiceExecutable(String executableName, Uri downloadUrl)
       at OpenQA.Selenium.IE.InternetExplorerDriverService.CreateDefaultService()
       at OpenQA.Selenium.IE.InternetExplorerDriver..ctor(InternetExplorerOptions options)
       at OpenQA.Selenium.IE.InternetExplorerDriver..ctor()
       at Accelrys.CommonTestFramework.WebActions.WebActionLibrary.CreateSeleniumDriver()