System.Net.WebClient exception calling UploadValues with encoded string containing single quote

I get the following exception when calling UploadValues with an encoded string containing a single quote:

An exception of type 'System.Net.WebException' occurred in System.dll but was not handled in user code

Additional information: The remote server returned an error: (500) Internal Server Error.

The code is running in the following action of an ASP.NET MVC web site:

   public class HomeController : Controller
    {
        public string Index()
        {
            var welcomeMessage = string.Empty;

            using (var client = new WebClient())
            {
                var encodedName = HttpUtility.HtmlEncode("Dave's");
                var nameValue = new NameValueCollection { { "name", encodedName } };

                var result = client.UploadValues("http://localhost:54011/Services/GetString", nameValue);

                welcomeMessage = System.Text.Encoding.UTF8.GetString(result);
            }

            return welcomeMessage;
        }
}

The GetString action is defined like this:

public class ServicesController : Controller
{
    public string GetString(string name)
    {
        return "Hello " + name;
    }
}

If I remove the single quote the method succeeds. How can I pass a string with quotes to UploadValues?