Using C# 4.0 and dynamic to parse JSON

本文轉載自查看原文 2012-09-14 17:14 6861 dynamic parse JSON C#

An alternative deserialisation approach is suggested here. I modified the code slightly to fix a bug and suit my coding style. All you need is this:

View Code

  1 using System;
  2 using System.Collections;
  3 using System.Collections.Generic;
  4 using System.Collections.ObjectModel;
  5 using System.Dynamic;
  6 using System.Linq;
  7 using System.Text;
  8 using System.Web.Script.Serialization;
  9
10 private sealed class DynamicJsonConverter : JavaScriptConverter
11 {
12      public override object Deserialize(IDictionary< string, object> dictionary, Type type, JavaScriptSerializer serializer)
13     {
14          if (dictionary == null)
15              throw new ArgumentNullException( " dictionary ");
16
17          return type == typeof( object) ? new DynamicJsonObject(dictionary) : null;
18     }
19
20      public override IDictionary< string, object> Serialize( object obj, JavaScriptSerializer serializer)
21     {
22          throw new NotImplementedException();
23     }
24
25      public override IEnumerable<Type> SupportedTypes
26     {
27          get { return new ReadOnlyCollection<Type>( new List<Type>( new[] { typeof( object) })); }
28     }
29
30      #region Nested type: DynamicJsonObject
31
32      private sealed class DynamicJsonObject : DynamicObject
33     {
34          private readonly IDictionary< string, object> _dictionary;
35
36          public DynamicJsonObject(IDictionary< string, object> dictionary)
37         {
38              if (dictionary == null)
39                  throw new ArgumentNullException( " dictionary ");
40             _dictionary = dictionary;
41         }
42
43          public override string ToString()
44         {
45              var sb = new StringBuilder( " { ");
46             ToString(sb);
47              return sb.ToString();
48         }
49
50          private void ToString(StringBuilder sb)
51         {
52              var firstInDictionary = true;
53              foreach ( var pair in _dictionary)
54             {
55                  if (!firstInDictionary)
56                     sb.Append( " , ");
57                 firstInDictionary = false;
58                  var value = pair.Value;
59                  var name = pair.Key;
60                  if (value is string)
61                 {
62                     sb.AppendFormat( " {0}:\"{1}\" ", name, value);
63                 }
64                  else if (value is IDictionary< string, object>)
65                 {
66                      new DynamicJsonObject((IDictionary< string, object>)value).ToString(sb);
67                 }
68                  else if (value is ArrayList)
69                 {
70                     sb.Append(name + " :[ ");
71                      var firstInArray = true;
72                      foreach ( var arrayValue in (ArrayList)value)
73                     {
74                          if (!firstInArray)
75                             sb.Append( " , ");
76                         firstInArray = false;
77                          if (arrayValue is IDictionary< string, object>)
78                              new DynamicJsonObject((IDictionary< string, object>)arrayValue).ToString(sb);
79                          else if (arrayValue is string)
80                             sb.AppendFormat( " \"{0}\" ", arrayValue);
81                          else
82                             sb.AppendFormat( " {0} ", arrayValue);
83
84                     }
85                     sb.Append( " ] ");
86                 }
87                  else
88                 {
89                     sb.AppendFormat( " {0}:{1} ", name, value);
90                 }
91             }
92             sb.Append( " } ");
93         }
94
95          public override bool TryGetMember(GetMemberBinder binder, out object result)
96         {
97              if (!_dictionary.TryGetValue(binder.Name, out result))
98             {
99                  // return null to avoid exception.  caller can check for null this way...
100                 result = null;
101                  return true;
102             }
103
104              var dictionary = result as IDictionary< string, object>;
105              if (dictionary != null)
106             {
107                 result = new DynamicJsonObject(dictionary);
108                  return true;
109             }
110
111              var arrayList = result as ArrayList;
112              if (arrayList != null && arrayList.Count > 0)
113             {
114                  if (arrayList[ 0] is IDictionary< string, object>)
115                     result = new List< object>(arrayList.Cast<IDictionary< string, object>>().Select(x => new DynamicJsonObject(x)));
116                  else
117                     result = new List< object>(arrayList.Cast< object>());
118             }
119
120              return true;
121         }
122     }
123
124      #endregion
125 }

You can use it like this:

View Code

1 string json = ...;
2
3 var serializer = new JavaScriptSerializer();
4 serializer.RegisterConverters( new[] { new DynamicJsonConverter() });
5
6 dynamic obj = serializer.Deserialize(json, typeof( object));

So, given a JSON string:

View Code

1 {
2    " Items ":[
3     { " Name ": " Apple ", " Price ": 12.3 },
4     { " Name ": " Grape ", " Price ": 3.21 }
5   ],
6    " Date ": " 21/11/2010 "
7 }

The following code will work at runtime:

View Code

1 var data = serializer.Deserialize(json, typeof( object));
2
3 data.Date; // "21/11/2010"
4 data.Items.Count; // 2
5 data.Items[ 0].Name; // "Apple"
6 data.Items[ 0].Price; // 12.3 (as a decimal)
7 data.Items[ 1].Name; // "Grape"
8 data.Items[ 1].Price; // 3.21 (as a decimal)

I'm interested in any discussion about this approach.

EDIT

I updated the code to fix a small bug (with lists of complex types) and to include a ToString method that outputs the JSON string, which I found useful for debugging. You can drop the two methods out if you don't want them as they aren't required for deserialisation.

It's pretty simple using Newtonsoft.Json:

View Code

1 var jsonSerializer = new JsonSerializer();
2 dynamic stuff = jsonSerializer.Deserialize( new JsonTextReader( new StringReader( " { 'Name': 'Jon Smith', 'Address': { 'City': 'New York', 'State': 'NY' }, 'Age': 42 } ")));
3
4 var name = stuff.Name;
5 var address = stuff.Address.City;

.Net 4.0 has a built-in library to do this:

View Code

1 using System.Web.Script.Serialization;
2 JavaScriptSerializer jss = new JavaScriptSerializer();
3 var d=jss.Deserialize<dynamic>(str);

This is the simplest way You can use it like this:

View Code

1  (new System.Collections.Generic.Mscorlib_DictionaryDebugView<string,object>(((System.Collections.Generic.Dictionary<string,object>)(obj[0])))).Items[1]

refer to：

http://stackoverflow.com/questions/3142495/deserialize-json-into-c-sharp-dynamic-object

這有一篇介紹動態解析原理的文章：http://www.codeproject.com/Articles/349646/Dynamic-JSON-parser

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