.net 4中使用 dynamic,将json字符串转成对象的 万能方法。

在.net 4中增加了对弱类型的支持。为和弱类型的对象进行数据交换提供了方法。我们常常会遇到将json字符串转成对象的情景，虽然可以使用

JavaScriptSerializer 或者 
DataContractJsonSerializer

但是仍然需要些个对应的实体类，非常的麻烦。我在网上查资料，找到另外的实现方法：
使用：

string json = "[{\"name\":\"zhang3\"},{\"name\":\"zhang4\"}]";

var j = new JsonParser().FromJson(json);
//j是个 object[]
int len = j.Length;
var obj1 = j[0];
var name = j[1].name;

注意这里用到 dynamic 类型。在这里，弱类型的威力凸显出来了。

我们看看具体的实现类：

/// <summary>
/// json转换
/// </summary>
public class JsonParser {

/// <summary>
/// 从json字符串到对象。
/// </summary>
/// <param name="jsonStr"></param>
/// <returns></returns>
public dynamic FromJson(string jsonStr) {
JavaScriptSerializer jss = new JavaScriptSerializer();
jss.RegisterConverters(new JavaScriptConverter[] { new DynamicJsonConverter() });

dynamic glossaryEntry = jss.Deserialize(jsonStr, typeof(object)) as dynamic;
return glossaryEntry;
}
}

public class DynamicJsonConverter : JavaScriptConverter
{
public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
{
if (dictionary == null)
throw new ArgumentNullException("dictionary");

if (type == typeof(object))
{
return new DynamicJsonObject(dictionary);
}

return null;
}

public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
{
throw new NotImplementedException();
}

public override IEnumerable<Type> SupportedTypes
{
get { return new ReadOnlyCollection<Type>(new List<Type>(new Type[] { typeof(object) })); }
}
}

public class DynamicJsonObject : DynamicObject
{
private IDictionary<string, object> Dictionary { get; set; }

public DynamicJsonObject(IDictionary<string, object> dictionary)
{
this.Dictionary = dictionary;
}

public override bool TryGetMember(GetMemberBinder binder, out object result)
{
result = this.Dictionary[binder.Name];

if (result is IDictionary<string, object>)
{
result = new DynamicJsonObject(result as IDictionary<string, object>);
}
else if (result is ArrayList && (result as ArrayList) is IDictionary<string, object>)
{
result = new List<DynamicJsonObject>((result as ArrayList).ToArray().Select(x => new DynamicJsonObject(x as IDictionary<string, object>)));
}
else if (result is ArrayList)
{
result = new List<object>((result as ArrayList).ToArray());
}

return this.Dictionary.ContainsKey(binder.Name);
}
}

参考：

http://www.codeproject.com/Articles/349646/Dynamic-JSON-parser

http://msdn.microsoft.com/zh-cn/library/dd264736.aspx

http://www.oschina.net/question/89964_45078

http://stackoverflow.com/questions/6201529/turn-c-sharp-object-into-a-json-string-in-net-4