WriteJson: Object reference not set to an instance of an object.

[douglasg14b]

Bug description

Small model, trying to add a new entity. EF Core odly enough throws a null ref exception.

The last stack frame is at:

            if (value is not null)
            {
                var jsonValueReaderWriter = property.GetJsonValueReaderWriter() ?? property.GetTypeMapping().JsonValueReaderWriter;
                Check.DebugAssert(jsonValueReaderWriter is not null, "Missing JsonValueReaderWriter on JSON property");
                jsonValueReaderWriter.ToJson(writer, value);
            }

The result of property.GetJsonValueReaderWriter() ?? property.GetTypeMapping().JsonValueReaderWriter; is null for a dictionary?

Your code

builder.Services.AddDbContext<AppDbContext>(options =>
            options.UseNpgsql(appConfig.ConnectionString)
        );



var entity = new ReqResEntity(enrichedData);
db.ReqResData.Add(entity);
await db.SaveChangesAsync();





public class AppDbContext : DbContext
{
    public DbSet<ReqResEntity> ReqResData { get; set; }

    public AppDbContext(DbContextOptions<AppDbContext> options) : base(options) { }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<ReqResEntity>()
            .OwnsOne(x => x.RequestUrl, model => model.ToJson())
            .OwnsOne(x => x.SourceUrl, model => model.ToJson())
            .OwnsOne(x => x.Response, model => model.ToJson())
            .OwnsOne(x => x.Request, model => model.ToJson());
    }
}




public class ReqResEntity
{
    public int Id { get; set; }

    public DateTimeOffset TimeStamp { get; set; }

    public UrlDetailsEntity SourceUrl { get; set; }
    public UrlDetailsEntity RequestUrl { get; set; }
    public RequestEntity? Request { get; set; }
    public ResponseEntity? Response { get; set; }

    public string Agent { get; set; }
    public string Protocol { get; set; }
    public string HttpMethod { get; set; }
    public string? StatusCode { get; set; }


    private ReqResEntity() { }

    public ReqResEntity(EnrichedReqResData data)
    {
        TimeStamp = data.TimeStamp;
        SourceUrl = new UrlDetailsEntity(data.SourceUrl);
        RequestUrl = new UrlDetailsEntity(data.RequestUrl);
        Request = new RequestEntity(data.Request);
        Response = data.Response != null ? new ResponseEntity(data.Response) : null;
        Agent = data.Agent;
        Protocol = data.Protocol;
        HttpMethod = data.Request.HttpMethod;
        StatusCode = data.Response?.StatusCode.ToString() ?? null;
    }
}

public class UrlDetailsEntity
{
    public string Url { get; set; }
    public string Fqdn { get; set; }
    public string Tld { get; set; }
    public string Domain { get; set; }
    public string SubDomain { get; set; }

    public string Path { get; set; }
    public string Query { get; set; }

    private UrlDetailsEntity() { }

    public UrlDetailsEntity(UrlDetails urlDetails)
    {
        Url = urlDetails.Url;
        Fqdn = urlDetails.Fqdn;
        Tld = urlDetails.Tld;
        Domain = urlDetails.Domain;
        SubDomain = urlDetails.SubDomain;
        Path = urlDetails.Path;
        Query = urlDetails.Query;
    }
}

public class RequestEntity
{
    public DateTimeOffset TimeStamp { get; set; }
    public Dictionary<string, string> Headers { get; set; }
    public bool IsComplete { get; set; }
    public string? ContentType { get; set; }

    public int BodySize { get; set; }

    private RequestEntity() { }

    public RequestEntity(EnrichedRequest request)
    {
        TimeStamp = request.TimeStamp;
        Headers = request.Headers;
        IsComplete = request.IsComplete;
        ContentType = request.ContentType;

        BodySize = Encoding.Unicode.GetByteCount(request.Body);
    }
}

public class ResponseEntity
{
    public DateTimeOffset TimeStamp { get; set; }
    public string Reason { get; set; }
    public Dictionary<string, string> Headers { get; set; }
    public bool IsComplete { get; set; }
    public string? ContentType { get; set; }

    public int BodySize { get; set; }

    private ResponseEntity() { }

    public ResponseEntity(EnrichedResponse response)
    {
        TimeStamp = response.TimeStamp;
        Reason = response.Reason;
        Headers = response.Headers;
        IsComplete = response.IsComplete;
        ContentType = response.ContentType;

        BodySize = Encoding.Unicode.GetByteCount(response.Body);
    }
}

Stack traces

System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.WriteJson(Utf8JsonWriter writer, Object navigationValue, IUpdateEntry parentEntry, IEntityType entityType, Nullable`1 ordinal, Boolean isCollection, Boolean isTopLevel)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.<GenerateColumnModifications>g__HandleJson|41_4(List`1 columnModifications, <>c__DisplayClass41_0&)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.GenerateColumnModifications()
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.<>c.<get_ColumnModifications>b__33_0(ModificationCommand command)
   at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.get_ColumnModifications()
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlUpdateSqlGenerator.AppendInsertOperation(StringBuilder commandStringBuilder, IReadOnlyModificationCommand command, Int32 commandPosition, Boolean overridingSystemValue, Boolean& requiresTransaction)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlUpdateSqlGenerator.AppendInsertOperation(StringBuilder commandStringBuilder, IReadOnlyModificationCommand command, Int32 commandPosition, Boolean& requiresTransaction)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.AddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.TryAddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.CreateCommandBatches(IEnumerable`1 commandSet, Boolean moreCommandSets, Boolean assertColumnModification, ParameterNameGenerator parameterNameGenerator)+MoveNext()
   at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.BatchCommands(IList`1 entries, IUpdateAdapter updateAdapter)+MoveNext()
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList`1 entries, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList`1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Webbler.Web.WebApp.<>c.<<Build>b__0_1>d.MoveNext()

Verbose output

EF Core version

9.0.1

Database provider

Npgsql.EntityFrameworkCore.PostgreSQL

Target framework

.NET 9

Operating system

Windows 10

IDE

Rider