Introduction

This is a small article about an issue I had recently trying to save some big documents represented as .Net objects in MongoDB using the MongoDB .Net driver.

While saving a “relatively” big document I’ve received the following exception:

System.IO.FileFormatException: Size 32325140 is larger than MaxDocumentSize 16777216.
   at MongoDB.Bson.IO.BsonBinaryWriter.BackpatchSize() in c:\projects\mongo-csharp-driver\MongoDB.Bson\IO\BsonBinaryWriter.cs:line 697
   at MongoDB.Bson.IO.BsonBinaryWriter.WriteEndArray() in c:\projects\mongo-csharp-driver\MongoDB.Bson\IO\BsonBinaryWriter.cs:line 294
   at MongoDB.Bson.Serialization.Serializers.EnumerableSerializerBase`1.Serialize(BsonWriter bsonWriter, Type nominalType, Object value, IBsonSerializationOptions options) in c:\projects\mongo-csharp-driver\MongoDB.Bson\Serialization\Serializers\EnumerableSerializerBase.cs:line 408
   at MongoDB.Bson.Serialization.BsonClassMapSerializer.SerializeMember(BsonWriter bsonWriter, Object obj, BsonMemberMap memberMap) in c:\projects\mongo-csharp-driver\MongoDB.Bson\Serialization\Serializers\BsonClassMapSerializer.cs:line 684
   at MongoDB.Bson.Serialization.BsonClassMapSerializer.Serialize(BsonWriter bsonWriter, Type nominalType, Object value, IBsonSerializationOptions options) in c:\projects\mongo-csharp-driver\MongoDB.Bson\Serialization\Serializers\BsonClassMapSerializer.cs:line 432
   at MongoDB.Driver.Internal.MongoInsertMessage.AddDocument(BsonBuffer buffer, Type nominalType, Object document) in c:\projects\mongo-csharp-driver\MongoDB.Driver\Communication\Messages\MongoInsertMessage.cs:line 53
   at MongoDB.Driver.Operations.InsertOperation.Execute(MongoConnection connection) in c:\projects\mongo-csharp-driver\MongoDB.Driver\Operations\InsertOperation.cs:line 97
   at MongoDB.Driver.MongoCollection.InsertBatch(Type nominalType, IEnumerable documents, MongoInsertOptions options) in c:\projects\mongo-csharp-driver\MongoDB.Driver\MongoCollection.cs:line 1149
   at MongoDB.Driver.MongoCollection.Insert(Type nominalType, Object document, MongoInsertOptions options) in c:\projects\mongo-csharp-driver\MongoDB.Driver\MongoCollection.cs:line 1004
   at MongoDB.Driver.MongoCollection.Save(Type nominalType, Object document, MongoInsertOptions options) in c:\projects\mongo-csharp-driver\MongoDB.Driver\MongoCollection.cs:line 1426

Well the message is clear: seems like I’ve exceeded the MongoDB max document size threshold which is 16MB, fair enough this is quite a sane design decision.

First I’ll explain why I had this issue, then how I’ve solved it.

Continue reading →

Introduction

As you may know event handlers are a common source of memory leaks caused by the persistence of objects that are not used anymore, and you may think should have been collected, but are not, and for good reason.

In this (hopefully) short article, I’ll present the issue with event handlers in the context of the .Net framework, then I’ll show you how you can implement the standard solution to this issue, the weak event pattern, in two ways, either using:

the “legacy” (well, before .Net 4.5, so not that old) approach which is quite cumbersome to implement

the new approach provided by the .Net 4.5 framework which is as simple as it can be

(The source code is available here.)

Pragmateek

A geek on his way to IT pragmatism

Monthly Archives: March 2014

Reduce the size of MongoDB documents generated from .Net/C#

Introduction

The .Net weak event pattern in C#

Introduction