为什么Json.Encode没有正确编码从Json.Decode返回的数据？

Question

When using the Json class from System.Web.Helpers and I run the following code, I expected it to produce a json string containing the same information as the original string, but strangely it only returns the string { "employees" : {} } and omits the array entirely and replaces it with an empty object?

string jsonData = "{ \"employees\": [ { \"firstName\":\"John\" , \"lastName\":\"Doe\" }, { \"firstName\":\"Anna\" , \"lastName\":\"Smith\" }, { \"firstName\":\"Peter\" , \"lastName\":\"Jones\" } ] }";
var json = Json.Decode(jsonData);
string result = Json.Encode(json); 
// result is: { "employees" : {} }

When I look at the object returned from Json.Decode the array is decoded into a DynamicJsonArray. If I create a .NET object with arrays/lists/dictionaries it seems to encode them perfectly so the problem seems to be related to DynamicJsonArray.

If I encode/decode a complex json string without arrays it seems to be working fine:

string jsonData = "{ \"firstName\": \"John\", \"lastName\": \"Doe\", \"family\": { \"mother\": { \"firstName\": \"Anna\", \"lastName\": \"Smith\" }, \"father\": { \"firstName\": \"Peter\", \"lastName\": \"Jones\" }  }  }";
var json = Json.Decode(jsonData);
string result = Json.Encode(json); 
/* result is (formatted for readability):
{
    "firstName" : "John",
    "lastName" : "Doe",
    "family" : {
        "mother" : {
            "firstName" : "Anna",
            "lastName":"Smith"
         },
         "father" : {
             "firstName" : "Peter",
             "lastName" : "Jones"
          }
     }
}
*/

I have looked at the documentation on msdn but couldn't find any reasons why this shouldn't work. Could it be a bug or is it by design?

Update

If I have a json string that's an array at the root node, it encodes/decodes correctly so I really start to suspect that this is a bug (or at least it's very inconsistent):

string jsonData = "[ { \"firstName\":\"John\" , \"lastName\":\"Doe\" }, { \"firstName\":\"Anna\" , \"lastName\":\"Smith\" }, { \"firstName\":\"Peter\" , \"lastName\":\"Jones\" } ]";
var json = Json.Decode(jsonData);
string result = Json.Encode(json);
/* result is (formatted for readability):
[
    { 
        "firstName" : "John",
        "lastName" : "Doe"
    },
    {
        "firstName" : "Anna",
        "lastName" : "Smith" 
    },
    {
        "firstName" : "Peter",
        "lastName" : "Jones"
    }
]
*/

Update 2

I decided to open an issue with Microsoft after all. Let's see what they have to say: http://connect.microsoft.com/VisualStudio/feedback/details/779119/data-from-json-decode-is-not-encoded-correctly-when-encoding-with-json-encode

Answer 1

I'm experiencing this bug too, luckily the library is now open source so we can fix the bug ourselves: https://aspnetwebstack.codeplex.com/SourceControl/latest

The fix is in System.Web.Helpers/DynamicJavaScriptConverter.cs

// Get the value for each member in the dynamic object
foreach (string memberName in memberNames)
{
    //replace this line
    //values[memberName] = DynamicHelper.GetMemberValue(obj, memberName);

    //with this code
    var value = DynamicHelper.GetMemberValue(obj, memberName);
    if (value is DynamicJsonArray)
        value = (object[])(DynamicJsonArray)value;
    values[memberName] = value;
}

I've filed a bug with the suggested fix on the codeplex site: https://aspnetwebstack.codeplex.com/workitem/1085

Answer 2

I think you should be using Json.NET instead. See: Json.NET on Codeplex

Answer 3

Have you thought about creating and using classes, which you then can serialize / deserialize them?

JavaScriptSerializer serializer = new JavaScriptSerializer();
// to JSON
string json = serializer.Serialize(EmployeeList);
// from JSON
EmployeeList employeeList = serializer.Deserialize<EmployeeList>(json);

I almost always serialize / deserialize, because I need the data as an object for use during execution. But I guess that depends on your case.