在WCF中需要对象时，将JSON枚举从JSON反序列化为C＃

Question

I have a filter object in C#, that contains a dictionary of strings (that represent the propery name) and the corresponding value (expecting an object).

When sending an object of a custom type with JSON to WCF, I use __type in my JSON to deserialize correctly from the JSON object to a C# object. However, when sending a enum (represented as integer in JSON) this will be serialized as integer in C#, because the deserializer has no way of telling what kind of enum it is expecting.

The JSON I send:

{
    "filterList": [
        { "FilterProperty": "Status", "FilterValue": 4 }
        { "FilterProperty": "Status", "FilterValue": 6 }
    ]
}    

The DataContract it deserializes to a list of these:

public class Filter
{
        [DataMember]
        public string FilterProperty { get; set; }
        [DataMember]
        public object FilterValue { get; set; }
}

The FilterValue corresponds in this specific situation with the an enum. But because the FilterValue property is defined as object, the deserializer does not know how to deserialize it without additional information.

Is it possible to send additional information with JSON to let WCF correctly deserialize the enum even if an object is expected?

Or is the only way to solve this to use reflection to resolve the type from the filter property name?

Answer 1

No, there is no extra information you can embed in the JSON to instruct deserializers to set the type of a property of type object to anything other than object .

If you need to be able to support multiple types polymorphically across the WCF service boundary you can define an interface to represent your type, in this case something like IFilterValue , and then use the ServiceKnownType attribute to tell WCF about the supported implementations of the interface.

Hope this is of help.

EDIT

It seems to me another more interoperable solution would be to do something like:

public class Filter
{
    [DataMember]
    public string FilterProperty { get; set; }

    [DataMember]
    public string Type { get; set; }

    [DataMember]
    public string FilterValue { get; set; }
}

This means that rather than unboxing an object you can do an explicit string conversion which strikes me as a better option.