要实现有时候用Json.Net，有时候用默认实现，那么就要保证系统中两种实现并存。对于Server将对象序列化成Json传给Client很简单，我们只需要建立一个新的ActionResult，我们命名为JsonNetResult，然后在Get时，return这个JsonNetResult即可。JsonNetResult的代码实现为：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace MvcJsonNet
{
using System.IO;
using System.Web;
using System.Web.Mvc;
using Newtonsoft.Json;
public class JsonNetResult : JsonResult
{
public JsonNetResult()
{
Settings = new JsonSerializerSettings
{
ReferenceLoopHandling = ReferenceLoopHandling.Error
};
}
public JsonNetResult(object data,JsonRequestBehavior behavior = JsonRequestBehavior.AllowGet,string contentType=null,Encoding contentEncoding=null)
{
this.Data = data;
this.JsonRequestBehavior = behavior;
this.ContentEncoding = contentEncoding;
this.ContentType = contentType;
}
public JsonSerializerSettings Settings { get; private set; }
public override void ExecuteResult(ControllerContext context)
{
if (context == null)
throw new ArgumentNullException("context");
if (this.JsonRequestBehavior == JsonRequestBehavior.DenyGet
&& string.Equals(context.HttpContext.Request.HttpMethod,"GET",StringComparison.OrdinalIgnoreCase))
throw new InvalidOperationException("JSON GET is not allowed");
HttpResponseBase response = context.HttpContext.Response;
response.ContentType =
string.IsNullOrEmpty(this.ContentType) ? "application/json" : this.ContentType;
if (this.ContentEncoding != null)
response.ContentEncoding = this.ContentEncoding;
if (this.Data == null)
return;
var scriptSerializer = JsonSerializer.Create(this.Settings);
using (var sw = new StringWriter())
{
scriptSerializer.Serialize(sw,this.Data);
response.Write(sw.ToString());
}
}
}
}
[HttpGet]
public ActionResult GetJsonNet()
{
var myClass = InitClass();
return new JsonNetResult(myClass);
}
这是Get方法，但是对于ClientPost一个Json回Server，那么就比较麻烦了，需要修改好几处地方：
1，建立Json.Net的ValueProviderFactory，这个类主要就是用于Json字符串的反序列化。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace MvcJsonNet
{
using System.Collections;
using System.Dynamic;
using System.Globalization;
using System.IO;
using System.Web.Mvc;
using System.Web.Script.Serialization;
using Newtonsoft.Json;
public class JsonNetValueProviderFactory : ValueProviderFactory
{
private void AddToBackingStore(Dictionary<string,object> backingStore,string prefix,object value)
{
IDictionary<string,object> d = value as IDictionary<string,object>;
if (d != null)
{
foreach (KeyValuePair<string,object> entry in d)
{
AddToBackingStore(backingStore,MakePropertyKey(prefix,entry.Key),entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore,MakeArrayKey(prefix,i),l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json",StringComparison.InvariantCultureIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
// 接下来的代码是关键，判断content type，如果是json.net，那么就使用Json.Net的反序列化方法，
// 如果不是，那么就使用系统默认的反序列化方法
if (controllerContext.HttpContext.Request.ContentType.StartsWith(
"application/json.net",StringComparison.InvariantCultureIgnoreCase))
{
var jsonData = JsonConvert.DeserializeObject<ExpandoObject>(bodyText);
return jsonData;
}
else
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string,object> backingStore = new Dictionary<string,object>
(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore,String.Empty,jsonData);
return new DictionaryValueProvider<object>(backingStore,CultureInfo.CurrentCulture);
}
private string MakeArrayKey(string prefix,int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private string MakePropertyKey(string prefix,string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
}
2，在初始化MVC时替换掉默认的JsonValueProviderFactory。
在Global.asax的Application_Start时，写入以下代码：
ValueProviderFactories.Factories.Remove( ValueProviderFactories.Factories.OfType<JsonValueProviderFactory>().FirstOrDefault()); ValueProviderFactories.Factories.Add(new JsonNetValueProviderFactory());
3，建立新的ModelBinder，命名为JsonNetModelBinder。
namespace MvcJsonNet
{
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Web.Mvc;
using Newtonsoft.Json;
public class JsonNetModelBinder : DefaultModelBinder
{
protected override void BindProperty(ControllerContext controllerContext,ModelBindingContext bindingContext,PropertyDescriptor propertyDescriptor)
{
Debug.WriteLine("BindProperty");
if (!controllerContext.HttpContext.Request.ContentType.StartsWith(
"application/json.net",StringComparison.InvariantCultureIgnoreCase))
{
// 根据Content type来判断，只有json.net这种content type的才会使用该ModelBinder，
// 否则使用默认的Binder
base.BindProperty(controllerContext,bindingContext,propertyDescriptor);
return;
}
// need to skip properties that aren't part of the request,else we might hit a
// StackOverflowException
string name = propertyDescriptor.Name;
foreach (object attribute in propertyDescriptor.Attributes)
{
if (attribute is JsonPropertyAttribute)
{
var jp = attribute as JsonPropertyAttribute;
name = jp.PropertyName;
}
}
string fullPropertyKey = CreateSubPropertyName(bindingContext.ModelName,name);
if (!bindingContext.ValueProvider.ContainsPrefix(fullPropertyKey))
{
return;
}
// call into the property's model binder
IModelBinder propertyBinder = Binders.GetBinder(propertyDescriptor.PropertyType);
object originalPropertyValue = propertyDescriptor.GetValue(bindingContext.Model);
ModelMetadata propertyMetadata = bindingContext.PropertyMetadata[propertyDescriptor.Name];
propertyMetadata.Model = originalPropertyValue;
var innerBindingContext = new ModelBindingContext
{
ModelMetadata = propertyMetadata,ModelName = fullPropertyKey,ModelState = bindingContext.ModelState,ValueProvider = bindingContext.ValueProvider
};
object newPropertyValue = GetPropertyValue(controllerContext,innerBindingContext,propertyDescriptor,propertyBinder);
propertyMetadata.Model = newPropertyValue;
// validation
ModelState modelState = bindingContext.ModelState[fullPropertyKey];
if (modelState == null || modelState.Errors.Count == 0)
{
if (OnPropertyValidating(controllerContext,newPropertyValue))
{
SetProperty(controllerContext,newPropertyValue);
OnPropertyValidated(controllerContext,newPropertyValue);
}
}
else
{
SetProperty(controllerContext,newPropertyValue);
// Convert FormatExceptions (type conversion failures) into InvalidValue messages
foreach (
ModelError error in
modelState.Errors.Where(err => String.IsNullOrEmpty(err.ErrorMessage)
&& err.Exception != null)
.ToList())
{
for (Exception exception = error.Exception; exception != null;
exception = exception.InnerException)
{
if (exception is FormatException)
{
string displayName = propertyMetadata.GetDisplayName();
string errorMessageTemplate = "The value '{0}' is not valid for {1}.";
string errorMessage = String.Format(CultureInfo.CurrentCulture,errorMessageTemplate,modelState.Value.AttemptedValue,displayName);
modelState.Errors.Remove(error);
modelState.Errors.Add(errorMessage);
break;
}
}
}
}
}
}
}
4，建立一个VModel的基类，为该基类添加Attribute，然后在Global中添加Model和Binder的映射。
[ModelBinder(typeof (JsonNetModelBinder))]
public abstract class VEntity
{
public virtual long Id { get; set; }
}
Global.asax中Application_Start添加代码：
ModelBinders.Binders.Add(typeof(VEntity),new JsonNetModelBinder());
5在前端Post Json时，指定content type为application/json.net
function PostJsonNet() {
var jsonstr = $("#jsonstring")[0].innerHTML;
$.ajax({
url: "MyTest/CreateFromJsonNet",type: "POST",data: jsonstr,contentType: "application/json.net",dataType: "json",success: function (data) {
alert(data);
}
});
}
我们这样处理后，Client在往Server传送Json数据时，如果指定了contentType是application/json，那么就使用系统默认的方法来反序列化对象，如果是application/json.net，那么就使用Json.Net来反序列化。