Partial ObjectContext Auditing Example using SaveChanges hiding and ObjectStateManager

ContextExtensions.cs

public partial class YourEntities
  {
        public bool AuditAutoUserAndDateBypass { get; set; }
        public bool AuditBypass { get; set; }
        public string AuditProcess { get; set; }
        public string AuditSource { get; set; }
        public int AuditUser { get; set; }

        partial void OnContextCreated()
        {
            this.AuditAutoUserAndDateBypass = false;
            this.AuditBypass = false;
            if (this.AuditSource == null) this.AuditSource = "No Source";
            if (this.AuditProcess == null) this.AuditProcess = "No Process";
        }

        public new int SaveChanges()
        {
            var r = 0;

            this.DetectChanges();

            var auditList = new List<AuditLog>();

            // ComplexTypes

            var relations = this.ObjectStateManager.GetObjectStateEntries(~EntityState.Detached).Where(e => e.IsRelationship);
            foreach (var entry in relations)
            {
                if (AuditAutoUserAndDateBypass) continue;

                var fieldsMetaData = entry.CurrentValues.DataRecordInfo.FieldMetadata;

                #region CreatedBy

                var createdUser = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "CreatedBy");
                if (createdUser.FieldType != null)
                {
                    string fieldTypeName = createdUser.FieldType.TypeUsage.EdmType.Name;
                    if (fieldTypeName == PrimitiveTypeKind.Int32.ToString())
                    {
                        entry.CurrentValues.SetInt32(createdUser.Ordinal, this.AuditUser);
                    }
                }

                #endregion CreatedBy

                #region CreatedDate

                var createdDate = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "CreatedDate");
                if (createdDate.FieldType != null)
                {
                    string fieldTypeName = createdDate.FieldType.TypeUsage.EdmType.Name;
                    if (fieldTypeName == PrimitiveTypeKind.DateTime.ToString())
                    {
                        entry.CurrentValues.SetDateTime(createdDate.Ordinal, DateTime.Now);
                    }
                }

                #endregion CreatedDate

                #region ActiveFlag

                var activeFlag = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "ActiveFlag");
                if (activeFlag.FieldType != null)
                {
                    string fieldTypeName = activeFlag.FieldType.TypeUsage.EdmType.Name;
                    if (fieldTypeName == PrimitiveTypeKind.Boolean.ToString())
                    {
                        entry.CurrentValues.SetBoolean(activeFlag.Ordinal, true);
                    }
                }

                #endregion ActiveFlag
            }

            // Inserts

            var added = this.ObjectStateManager.GetObjectStateEntries(EntityState.Added);
            foreach (var entry in added)
            {
                if (AuditAutoUserAndDateBypass) continue;

                var fieldsMetaData = entry.CurrentValues.DataRecordInfo.FieldMetadata;

                #region CreatedBy

                var createdUser = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "CreatedBy");
                if (createdUser.FieldType != null)
                {
                    string fieldTypeName = createdUser.FieldType.TypeUsage.EdmType.Name;
                    if (fieldTypeName == PrimitiveTypeKind.Int32.ToString())
                    {
                        entry.CurrentValues.SetInt32(createdUser.Ordinal, this.AuditUser);
                    }
                }

                #endregion CreatedBy

                #region CreatedDate

                var createdDate = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "CreatedDate");
                if (createdDate.FieldType != null)
                {
                    string fieldTypeName = createdDate.FieldType.TypeUsage.EdmType.Name;
                    if (fieldTypeName == PrimitiveTypeKind.DateTime.ToString())
                    {
                        entry.CurrentValues.SetDateTime(createdDate.Ordinal, DateTime.Now);
                    }
                }

                #endregion CreatedDate

                #region ActiveFlag

                var activeFlag = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "ActiveFlag");
                if (activeFlag.FieldType != null)
                {
                    string fieldTypeName = activeFlag.FieldType.TypeUsage.EdmType.Name;
                    if (fieldTypeName == PrimitiveTypeKind.Boolean.ToString())
                    {
                        entry.CurrentValues.SetBoolean(activeFlag.Ordinal, true);
                    }
                }

                #endregion ActiveFlag
            }

            // Deletes

            var deleted = this.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted);
            foreach (var entry in deleted)
            {
                if (!IsAuditable(entry)) continue;

                var list = AuditObject.AuditObjectDeletedFactory(entry, this.AuditUser, this.AuditSource, this.AuditProcess);
                auditList.AddRange(list.Select(ToAuditLog));
            }

            // Updates

            var modified = this.ObjectStateManager.GetObjectStateEntries(EntityState.Modified);
            foreach (var entry in modified)
            {
                if (!AuditAutoUserAndDateBypass)
                {
                    var fieldsMetaData = entry.CurrentValues.DataRecordInfo.FieldMetadata;

                    #region ModifiedBy

                    var modifiedUser = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "ModifiedBy");
                    if (modifiedUser.FieldType != null)
                    {
                        string fieldTypeName = modifiedUser.FieldType.TypeUsage.EdmType.Name;
                        if (fieldTypeName == PrimitiveTypeKind.Int32.ToString())
                        {
                            entry.CurrentValues.SetInt32(modifiedUser.Ordinal, this.AuditUser);
                        }
                    }

                    #endregion ModifiedBy

                    #region ModifiedDate

                    var modifiedDate = fieldsMetaData.FirstOrDefault(f => f.FieldType.Name == "ModifiedDate");
                    if (modifiedDate.FieldType != null)
                    {
                        string fieldTypeName = modifiedDate.FieldType.TypeUsage.EdmType.Name;
                        if (fieldTypeName == PrimitiveTypeKind.DateTime.ToString())
                        {
                            entry.CurrentValues.SetDateTime(modifiedDate.Ordinal, DateTime.Now);
                        }
                    }

                    #endregion ModifiedDate
                }

                if (IsAuditable(entry))
                {
                    var list = AuditObject.AuditObjectModifiedFactory(entry, this.AuditUser, this.AuditSource, this.AuditProcess);
                    auditList.AddRange(list.Select(ToAuditLog));
                }
            }

            if (auditList.Count > 0 && !AuditBypass)
            {
                auditList.ForEach(c => this.AuditLogs.AddObject(c));
            }

            r = base.SaveChanges();

            // Get Identity Keys for Added

            if (r > 0)
            {
                var count = 0;

                foreach (var entry in added)
                {
                    if (!IsAuditable(entry) || AuditBypass) continue;

                    var add = AuditObject.AuditObjectAddedFactory(entry, this.AuditUser, this.AuditSource, this.AuditProcess);
                    if (add == null) continue;

                    var a = ToAuditLog(add);
                    this.AuditLogs.AddObject(a);
                    count++;
                }

                if (count > 0)
                {
                    r = r + base.SaveChanges();
                }
            }

            return r;
        }
}