通过NameValuePairsValueProvider对象来获取指定前缀的Key

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Web.Http.ValueProviders.Providers;

 namespace ConsoleApp
 {
     internal class Program
     {
         private static void Main(string[] args)
         {
             var dic = new Dictionary<string, string>
             {
                 {"contact.Name", "张三"},
                 {"contact.PhoneNo", ""},
                 {"contact.EmailAddress", "zhangsan@gmail.com"},
                 {"contact.Address.Province", "上海"},
                 {"contact.Address.City", "上海"},
                 {"contact.Address.District", "长宁区"},
                 {"contact.Address.Street", "金钟路968号"}
             };
             var valueProvider = new NameValuePairsValueProvider(dic.ToArray(), null);

             // prefix=""
             Console.WriteLine("Prefix: <Empty>");
             Console.WriteLine("{0,-14}{1}", "key", "value");
             var keys = valueProvider.GetKeysFromPrefix(string.Empty);
             foreach (var item in keys)
             {
                 Console.WriteLine("{0,-14}{1}", item.Key, item.Value);
             }

             // Prefix="contact"
             Console.WriteLine("Prefix: contact");
             Console.WriteLine("{0,-14}{1}", "key", "value");
             keys = valueProvider.GetKeysFromPrefix("contact");
             foreach (var item in keys)
             {
                 Console.WriteLine("{0,-14}{1}", item.Key, item.Value);
             }

             // Prefix="contact"
             Console.WriteLine("Prefix: contact.Address");
             Console.WriteLine("{0,-14}{1}", "key", "value");
             keys = valueProvider.GetKeysFromPrefix("contact.Address");
             foreach (var item in keys)
             {
                 Console.WriteLine("{0,-14}{1}", item.Key, item.Value);
             }

             Console.Read();
         }
     }
 }