Using Selenium 2's IWebDriver to interact with elements on the page
As ZloiAdun mentions, there is a lovely new Select class in the OpenQA.Selenium.Support.UI namespace. That's one of the best ways to access a selection element and it's options because it's api is so easy. Let's say you've got a web page that looks something like this
<!DOCTYPE html><head><title>Disposable Page</title></head> <body > <select id="select"> <option value="volvo">Volvo</option> <option value="saab">Saab</option> <option value="mercedes">Mercedes</option> <option value="audi">Audi</option> </select> </body></html>You're code to access the select would look like this. Note how I create the Select object by passing a normal IWebElement to it's constructor. You have plenty of methods on the Select object. Take a look at the source for more information, until it gets properly documented.
using OpenQA.Selenium.Support.UI;using OpenQA.Selenium;using System.Collections.Generic;using OpenQA.Selenium.IE;namespace Selenium2{ class SelectExample { public static void Main(string[] args) { IWebDriver driver = new InternetExplorerDriver(); driver.Navigate().GoToUrl("www.example.com"); //note how here's i'm passing in a normal IWebElement to the Select // constructor Select select = new Select(driver.FindElement(By.Id("select"))); IList<IWebElement> options = select.GetOptions(); foreach (IWebElement option in options) { System.Console.WriteLine(option.Text); } select.SelectByValue("audi"); //This is only here so you have time to read the output and System.Console.ReadLine(); driver.Quit(); } }}A couple things to note about the Support class however. Even if you downloaded the latest beta, the support DLL won't be there. The Support package has a relatively long history in the Java libraries (that's where PageObject lives) but it's still pretty fresh in the .Net driver. Fortunately, it's really easy to build from source. I pulled from SVN then referenced the WebDriver.Common.dll from the beta download and built in C# Express 2008. This class hasn't been as well tested as some of the other classes, but my example worked in Internet Explorer and Firefox.
There's a few other things that I should point out based on your code above. Firstly the line you were using to find the select element
driver.FindElements(By.TagName("select"));is going to find all select elements. you should probably use driver.FindElement, without the 's'.
Also, very rarely would you use INavigation directly. You'll do most of your navigation like driver.Navigate().GoToUrl("http://example.com");
Lastly, DefaultSelenium is the way to access the older Selenium 1.x apis. Selenium 2 is a pretty significant departure from Selenium 1, so unless you're trying to migrate old tests to the new Selenium 2 api (often referred to as the WebDriver api) you won't use DefaultSelenium.
You should get all option elements from your select using ddl.FindElements(By.TagName("option"));. Then you can iterate through the returned collection and select required item(s) by using SetSelected method of the IWebElement
Update: It seems that there's now a C# implementation of the Select in WebDriver - previously it was in Java only. Please take a look at its code and it is easier to use this class