use Guids as id's

[eltjo-k]

The use of Guids as id's leads to the following types of exception when id's are converted to strings:

{System.InvalidCastException: Object must implement IConvertible.
   at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
   at Newtonsoft.Json.Linq.Extensions.Convert[T,U](T token)
   at Newtonsoft.Json.Linq.Extensions.Value[T,U](IEnumerable`1 value)
   at Newtonsoft.Json.Linq.Extensions.Value[U](IEnumerable`1 value)
   at Saule.Serialization.ResourceSerializer.<>c__DisplayClass23_0.<GetRelationshipData>b__0(IDictionary`2 props)
   at Saule.Serialization.ResourceSerializer.SerializeArrayOrObject(JToken token, Func`2 serializeObj)
   at Saule.Serialization.ResourceSerializer.GetRelationshipData(ResourceRelationship relationship, JToken relationshipValues)
   at Saule.Serialization.ResourceSerializer.SerializeRelationship(ResourceRelationship relationship, IDictionary`2 properties)
   at Saule.Serialization.ResourceSerializer.SerializeRelationships(IDictionary`2 properties)
   at Saule.Serialization.ResourceSerializer.SerializeData(IDictionary`2 properties)
   at Saule.Serialization.ResourceSerializer.SerializeArrayOrObject(JToken token, Func`2 serializeObj)
   at Saule.Serialization.ResourceSerializer.Serialize(JsonSerializer serializer)
   at Saule.JsonApiSerializer.Serialize(PreprocessResult result)
   at Saule.JsonApiSerializer`1.Serialize(Object object, Uri requestUri)
   at ...

This happens with:

• collections of objects with Guid-ids
• single objects with belongsTo-relations to objects with Guid-ids
• single objects with hasMany-relations to objects with Guid-ids.

Unit tests for these cases have been added.

These exceptions can be solved by replacing occurences of JToken.Value<string>() by cast operators that are explicitly defined for JToken's (see here). This cast operator throws exceptions if the JToken does not contain the proper datatypes as defined in this list, which seems to contain every type that might be used as an index. Finally it uses Convert.ToString(...) which first tries to convert through IConvertible, just like the JToken.Value<string>()-conversion method does, so this change should not break any existing working behaviour.

[joukevandermaas]

Awesome work, thanks! I will create 1.4.2 with this fix in it.