Is this a bug in JSON.NET or Entity Framework or am I doing something wrong while trying to serialize a list of Exceptions with JSON.NET?

entity-framework-6 exception json.net serialization

Question

Got this error when trying to serialize a set of errors:

"ISerializable type 'System.Data.Entity.Infrastructure.DbUpdateConcurrencyException' does not have a valid constructor. To correctly implement ISerializable a constructor that takes SerializationInfo and StreamingContext parameters should be present."

The constructor is in fact present in the base classes, but it is a protected member.

Someone asked to see the JSON:

{
    "$type": "System.Data.Entity.Infrastructure.DbUpdateConcurrencyException, EntityFramework",
    "ClassName": "System.Data.Entity.Infrastructure.DbUpdateConcurrencyException",
    "Message": "Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=472540 for information on understanding and handling optimistic concurrency exceptions.",
    "Data": {
        "$type": "System.Collections.ListDictionaryInternal, mscorlib"
    },
    "InnerException": {
        "$type": "System.Data.Entity.Core.OptimisticConcurrencyException, EntityFramework",
        "ClassName": "System.Data.Entity.Core.OptimisticConcurrencyException",
        "Message": "Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=472540 for information on understanding and handling optimistic concurrency exceptions.",
        "Data": {
            "$type": "System.Collections.ListDictionaryInternal, mscorlib"
        },
        "InnerException": null,
        "HelpURL": null,
        "StackTraceString": "   at System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.ValidateRowsAffected(Int64 rowsAffected, UpdateCommand source)\r\n   at System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.Update()\r\n   at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.<Update>b__2(UpdateTranslator ut)\r\n   at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.Update[T](T noChangesResult, Func`2 updateFunction)\r\n   at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.Update()\r\n   at System.Data.Entity.Core.Objects.ObjectContext.<SaveChangesToStore>b__35()\r\n   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesToStore(SaveOptions options, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass2a.<SaveChangesInternal>b__27()\r\n   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesInternal(SaveOptions options, Boolean executeInExistingTransaction)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.SaveChanges(SaveOptions options)\r\n   at System.Data.Entity.Internal.InternalContext.SaveChanges()",
        "RemoteStackTraceString": null,
        "RemoteStackIndex": 0,
        "ExceptionMethod": "8\nValidateRowsAffected\nEntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\nSystem.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator\nVoid ValidateRowsAffected(Int64, System.Data.Entity.Core.Mapping.Update.Internal.UpdateCommand)",
        "HResult": -2146233087,
        "Source": "EntityFramework",
        "WatsonBuckets": null
    },
    "HelpURL": null,
    "StackTraceString": "   at System.Data.Entity.Internal.InternalContext.SaveChanges()\r\n   at System.Data.Entity.Internal.LazyInternalContext.SaveChanges()\r\n   at System.Data.Entity.DbContext.SaveChanges()\r\n   at REDACTED FOR DISPLAY ON STACKOVERFLOW",
    "RemoteStackTraceString": null,
    "RemoteStackIndex": 0,
    "ExceptionMethod": "8\nSaveChanges\nEntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\nSystem.Data.Entity.Internal.InternalContext\nInt32 SaveChanges()",
    "HResult": -2146233087,
    "Source": "EntityFramework",
    "WatsonBuckets": null,
    "SafeSerializationManager": {
        "$type": "System.Runtime.Serialization.SafeSerializationManager, mscorlib",
        "m_serializedStates": {
            "$type": "System.Collections.Generic.List`1[[System.Object, mscorlib]], mscorlib",
            "$values": [
                {
                    "$type": "System.Data.Entity.Infrastructure.DbUpdateException+DbUpdateExceptionState, EntityFramework",
                    "InvolvesIndependentAssociations": false
                }
            ]
        }
    },
    "CLR_SafeSerializationManager_RealType": "System.Data.Entity.Infrastructure.DbUpdateConcurrencyException, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
}

Here is example code that throws the exception:

var serializationSettings = new JsonSerializerSettings() {
    DateFormatHandling = DateFormatHandling.IsoDateFormat,
    DateParseHandling = DateParseHandling.DateTime,
    DateTimeZoneHandling = DateTimeZoneHandling.RoundtripKind,
    DefaultValueHandling = DefaultValueHandling.Include,
    TypeNameHandling = TypeNameHandling.All,
    TypeNameAssemblyFormat = System.Runtime.Serialization.Formatters.FormatterAssemblyStyle.Simple,
    ObjectCreationHandling = ObjectCreationHandling.Replace, //Necessary for subclassing list types
    ConstructorHandling = ConstructorHandling.AllowNonPublicDefaultConstructor
};

var json = JsonConvert.SerializeObject( new System.Data.Entity.Infrastructure.DbUpdateConcurrencyException( "hi" ), serializationSettings );
if (json == null)
    return null;
var err = JsonConvert.DeserializeObject<System.Data.Entity.Infrastructure.DbUpdateConcurrencyException>( json, serializationSettings ); //throws error

This gets even stranger, because as one answer points out, this is an exceptional class in that it does not directly implement a constructor with the expected signature. Instead, decompiling the class shows some kind of, quite literal, "justification" for NOT implementing the expected constructor...

/// <summary>
/// Exception thrown by <see cref="T:System.Data.Entity.DbContext" /> when the saving of changes to the database fails.
/// Note that state entries referenced by this exception are not serialized due to security and accesses to the
/// state entries after serialization will return null.
/// </summary>
[SuppressMessage("Microsoft.Design", "CA1032:ImplementStandardExceptionConstructors",
    Justification = "SerializeObjectState used instead")]
[Serializable]
public class DbUpdateException : DataException
{
    /// <summary>
    /// Holds exception state that will be serialized when the exception is serialized.
    /// </summary>
    [Serializable]
    private struct DbUpdateExceptionState : ISafeSerializationData
    {
1
2
3/10/2016 4:42:35 AM

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Popular Answer

According to the Json.net documentation,

ISerializable

Types that implement ISerializable are serialized as JSON objects. When serializing, only the values returned from ISerializable.GetObjectData are used; members on the type are ignored. When deserializing, the constructor with a SerializationInfo and StreamingContext is called, passing the JSON object's values.

In situations where this behavior is not wanted, the JsonObjectAttribute can be placed on a .NET type that implements ISerializable to force it to be serialized as a normal JSON object.

Since you don't owe the DbUpdateConcurrencyException class, A workaround could be to create a custom exception class which derive from the DbUpdateConcurrencyException and Mark it with attribute JsonObject.

    [JsonObject]
    class CustomException : DbUpdateConcurrencyException
    {
        public CustomException(string message) : base(message) { }
    }

     // Serialize the new customException
     var json = JsonConvert.SerializeObject(
         new CustomException("hi"), serializationSettings);

     //shall not throw error now
     DbUpdateConcurrencyException err = 
          JsonConvert.DeserializeObject<DbUpdateConcurrencyException>(json, serializationSettings);

This is a just a POC that I tried to make it work for JSON.Net. It makes no sense to create custom classes for all type which inherits ISerializable and doesn't have required constructor. May be you can try creating Castle core DynamicProxy generator to wrap the thrown exception which are ISerializable and mark them with JsonObject attribute on-the-fly before serializing them.

And you're right. Json.net is not able to find the protected constructor because inheritance goes like 

DbUpdateConcurrencyException <- DbUpdateException <- DataException

And DataException class have the Protected constructor which json.net is looking for. Every exception class in .Net framework which is derived from SystemException have this constructor as protected constructor but DbUpdateException && DbUpdateConcurrencyException doesn't have it. So you can guess who to blame now (IMO EF).

Following are the classes I found which have the standard serializable constructor missing and would throw exception during deserialization.

  • EntitySqlException
  • PropertyConstraintException
  • DbUpdateConcurrencyException
  • DbUpdateException
  • ToolingException
  • DbEntityValidationException
  • CommandLineException

I wrote this issue to EF team here.

2
3/9/2016 10:51:32 PM

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