how to create an audit trail with Entity framework 5 and MVC 4
I am building an MVC 4 application, using EF 5. I need to do an audit trail, ie log any changes that end users make.
I have asked this question a few times, but haven't really gotten a satisfying answer before. So I am adding a lot more details in hoping to get somewhere..
currently I have multiple repositories
ie
public class AuditZoneRepository : IAuditZoneRepository
{
private AISDbContext context = new AISDbContext();
public int Save(AuditZone model, ModelStateDictionary modelState)
{
if (model.Id == 0)
{
context.AuditZones.Add(model);
}
else
{
var recordToUpdate = context.AuditZones.FirstOrDefault(x => x.Id == model.Id);
if (recordToUpdate != null)
{
recordToUpdate.Description = model.Description;
recordToUpdate.Valid = model.Valid;
recordToUpdate.ModifiedDate = DateTime.Now;
}
}
try
{
context.SaveChanges();
return 1;
}
catch (Exception ex)
{
modelState.AddModelError("", "Database error has occured. Please try again later");
return -1;
}
}
}
public class PostcodesRepository : IPostcodesRepository
{
private AISDbContext context = new AISDbContext();
public int Save(Postcodes model, ModelStateDictionary modelState)
{
if (model.Id == 0)
{
context.Postcodes.Add(model);
}
else
{
var recordToUpdate = context.Postcodes.FirstOrDefault(x => x.Id == model.Id);
if (recordToUpdate != null)
{
recordToUpdate.Suburb = model.Suburb;
recordToUpdate.State = model.State;
recordToUpdate.Postcode = model.Postcode;
recordToUpdate.AuditZoneId = model.AuditZoneId;
recordToUpdate.ModifiedDate = DateTime.Now;
}
}
try
{
context.SaveChanges();
return 1;
}
catch (Exception ex)
{
modelState.AddModelError("", "Database error has occured. Please try again later");
return -1;
}
}
}
Now I know for me to add the code to check to see if there are any changes i need to add it in the try of the save. Before the context.SaveChanges().
But currently I have 10 repos. I don't really want to add code to 10 different places. As this code will do exactly the same thing. I want to somehow have a baseclass that the repos inherit from.
any help? any sample code? any pointers?
would be appreciated. I am sure other people would have done this before
I am mappying my keys, relationships and tables like so
public class AuditZoneMap : EntityTypeConfiguration<AuditZone>
{
public AuditZoneMap()
{
// Primary Key
HasKey(t => t.Id);
// Properties
Property(t => t.Description)
.HasMaxLength(100);
// Table & Column Mappings
ToTable("AuditZone");
Property(t => t.Id).HasColumnName("Id");
Property(t => t.Description).HasColumnName("Description");
Property(t => t.Valid).HasColumnName("Valid");
Property(t => t.CreatedDate).HasColumnName("CreatedDate");
Property(t => t.CreatedBy).HasColumnName("CreatedBy");
Property(t => t.ModifiedDate).HasColumnName("ModifiedDate");
Property(t => t.ModifiedBy).HasColumnName("ModifiedBy");
// Relationships
HasOptional(t => t.CreatedByUser)
.WithMany(t => t.CreatedByAuditZone)
.HasForeignKey(d => d.CreatedBy);
HasOptional(t => t.ModifiedByUser)
.WithMany(t => t.ModifiedByAuditZone)
.HasForeignKey(d => d.ModifiedBy);
}
}
Answer
What I recommend you is to use the ChangeTracker property in EF.
Inside your DBContext.cs you will have this:
public class DBContext : DbContext
{
public DBContext () : base("DatabaseName")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
}
public DbSet<YourPocoModelNameHere > YourPocoModelNameHere { get; set; }
// This is overridden to prevent someone from calling SaveChanges without specifying the user making the change
public override int SaveChanges()
{
throw new InvalidOperationException("User ID must be provided");
}
public int SaveChanges(int userId)
{
// Get all Added/Deleted/Modified entities (not Unmodified or Detached)
foreach (var ent in this.ChangeTracker.Entries().Where(p => p.State == System.Data.EntityState.Added || p.State == System.Data.EntityState.Deleted || p.State == System.Data.EntityState.Modified))
{
// For each changed record, get the audit record entries and add them
foreach (AuditLog x in GetAuditRecordsForChange(ent, userId))
{
this.AuditLogs.Add(x);
}
}
// Call the original SaveChanges(), which will save both the changes made and the audit records
return base.SaveChanges();
}
private List<AuditLog> GetAuditRecordsForChange(DbEntityEntry dbEntry, int userId)
{
List<AuditLog> result = new List<AuditLog>();
DateTime changeTime = DateTime.UtcNow;
// Get the Table() attribute, if one exists
//TableAttribute tableAttr = dbEntry.Entity.GetType().GetCustomAttributes(typeof(TableAttribute), false).SingleOrDefault() as TableAttribute;
TableAttribute tableAttr = dbEntry.Entity.GetType().GetCustomAttributes(typeof(TableAttribute), true).SingleOrDefault() as TableAttribute;
// Get table name (if it has a Table attribute, use that, otherwise get the pluralized name)
string tableName = tableAttr != null ? tableAttr.Name : dbEntry.Entity.GetType().Name;
// Get primary key value (If you have more than one key column, this will need to be adjusted)
var keyNames = dbEntry.Entity.GetType().GetProperties().Where(p => p.GetCustomAttributes(typeof(KeyAttribute), false).Count() > 0).ToList();
string keyName = keyNames[0].Name; //dbEntry.Entity.GetType().GetProperties().Single(p => p.GetCustomAttributes(typeof(KeyAttribute), false).Count() > 0).Name;
if (dbEntry.State == System.Data.EntityState.Added)
{
// For Inserts, just add the whole record
// If the entity implements IDescribableEntity, use the description from Describe(), otherwise use ToString()
foreach (string propertyName in dbEntry.CurrentValues.PropertyNames)
{
result.Add(new AuditLog()
{
AuditLogId = Guid.NewGuid(),
UserId = userId,
EventDateUTC = changeTime,
EventType = "A", // Added
TableName = tableName,
RecordId = dbEntry.CurrentValues.GetValue<object>(keyName).ToString(),
ColumnName = propertyName,
NewValue = dbEntry.CurrentValues.GetValue<object>(propertyName) == null ? null : dbEntry.CurrentValues.GetValue<object>(propertyName).ToString()
}
);
}
}
else if (dbEntry.State == System.Data.EntityState.Deleted)
{
// Same with deletes, do the whole record, and use either the description from Describe() or ToString()
result.Add(new AuditLog()
{
AuditLogId = Guid.NewGuid(),
UserId = userId,
EventDateUTC = changeTime,
EventType = "D", // Deleted
TableName = tableName,
RecordId = dbEntry.OriginalValues.GetValue<object>(keyName).ToString(),
ColumnName = "*ALL",
NewValue = (dbEntry.OriginalValues.ToObject() is IDescribableEntity) ? (dbEntry.OriginalValues.ToObject() as IDescribableEntity).Describe() : dbEntry.OriginalValues.ToObject().ToString()
}
);
}
else if (dbEntry.State == System.Data.EntityState.Modified)
{
foreach (string propertyName in dbEntry.OriginalValues.PropertyNames)
{
// For updates, we only want to capture the columns that actually changed
if (!object.Equals(dbEntry.OriginalValues.GetValue<object>(propertyName), dbEntry.CurrentValues.GetValue<object>(propertyName)))
{
result.Add(new AuditLog()
{
AuditLogId = Guid.NewGuid(),
UserId = userId,
EventDateUTC = changeTime,
EventType = "M", // Modified
TableName = tableName,
RecordId = dbEntry.OriginalValues.GetValue<object>(keyName).ToString(),
ColumnName = propertyName,
OriginalValue = dbEntry.OriginalValues.GetValue<object>(propertyName) == null ? null : dbEntry.OriginalValues.GetValue<object>(propertyName).ToString(),
NewValue = dbEntry.CurrentValues.GetValue<object>(propertyName) == null ? null : dbEntry.CurrentValues.GetValue<object>(propertyName).ToString()
}
);
}
}
}
// Otherwise, don't do anything, we don't care about Unchanged or Detached entities
return result;
}
}
This will use the following table in your DB:
USE [databasename]
GO
/****** Object: Table [dbo].[auditlog] Script Date: 06/01/2014 05:56:49 p. m. ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[auditlog](
[auditlogid] [uniqueidentifier] NOT NULL,
[userid] [int] NOT NULL,
[eventdateutc] [datetime] NOT NULL,
[eventtype] [char](1) NOT NULL,
[tablename] [nvarchar](100) NOT NULL,
[recordid] [nvarchar](100) NOT NULL,
[columnname] [nvarchar](100) NOT NULL,
[originalvalue] [nvarchar](max) NULL,
[newvalue] [nvarchar](max) NULL,
CONSTRAINT [PK_AuditLog] PRIMARY KEY NONCLUSTERED
(
[auditlogid] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
ALTER TABLE [dbo].[auditlog] WITH CHECK ADD CONSTRAINT [FK_auditlog_users] FOREIGN KEY([userid])
REFERENCES [dbo].[users] ([userid])
GO
ALTER TABLE [dbo].[auditlog] CHECK CONSTRAINT [FK_auditlog_users]
GO
With this all set then you will just need to call your dbContext.SaveChanges(here the userId);
Hope this will work for you... I use it in all my applications and works great!
Enjoy it.
Full code found here: https://jmdority.wordpress.com/2011/07/20/using-entity-framework-4-1-dbcontext-change-tracking-for-audit-logging/