代码演示 .NET 4.5 自带的 ReadonlyCollection 的使用

代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConfigurationLibrary
{public class ConfigElement{public int Id { get; set; }public string Value { get; set; }}
}

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConfigurationLibrary
{public class ConfigurationContainer{private ReadOnlyDictionary<string, ConfigElement> _configuration;private Dictionary<string, ConfigElement> _mutableConfiguration;public ReadOnlyDictionary<string, ConfigElement> Configuration{get{_configuration =new ReadOnlyDictionary<string, ConfigElement>(_mutableConfiguration);return _configuration;}}public ConfigurationContainer(){_mutableConfiguration = new Dictionary<string, ConfigElement>();_mutableConfiguration.Add("key", new ConfigElement { Id=1,  Value="value1"});_mutableConfiguration.Add("key1", new ConfigElement { Id = 1, Value = "value1" });_mutableConfiguration["key2"] = new ConfigElement { Id = 1, Value = "value1" };}public bool AddToConfiguration(string key, ConfigElement value){if (ConfigurationAllowed(key, value)){_mutableConfiguration.Add(key, value);return true;}return false;}private bool ConfigurationAllowed(string key, ConfigElement value){// Put in your checks and balances// here and return the appropriate resultreturn true;}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using ConfigurationLibrary;namespace ConfigurationUser
{public class ConfigurationConsumer{IReadOnlyDictionary<string, ConfigurationLibrary.ConfigElement> _config;public ConfigurationConsumer(){_config = new ConfigurationLibrary.ConfigurationContainer().Configuration;}public void DoSomething(){if (_config.ContainsKey("key")){// Do Something
                Console.WriteLine(string.Format("Did Something, Got - {0}",_config["key"].Value));}else{// Do Something Else.Console.WriteLine("Did Something Else");}}public void BeNaughtyWithConfiguration(){IDictionary<string, ConfigElement> convertToReadWrite= (IDictionary<string, ConfigElement>)_config;ConfigElement element = convertToReadWrite["key"];element.Value = "Haa Haa";Console.WriteLine(element.Value);Console.WriteLine(convertToReadWrite["key"].Value);Console.ReadLine();// 上面的代码都能运行通过，下面这行代码将抛出异常。convertToReadWrite.Add("Key12345", new ConfigElement { Id = 100, Value = "Haa Haa" });}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ReadOnlyCollectionSample
{class Program{static void Main(string[] args){ConfigurationUser.ConfigurationConsumer consumer =new ConfigurationUser.ConfigurationConsumer();consumer.DoSomething();Console.ReadLine();consumer.BeNaughtyWithConfiguration();}}
}