Keep track of when your entities change automatically, by implementing a couple of quick changes.
UPDATE 2016-07-07: Now includes async methods and improved null checking thanks to Tymek Majewski.
Add fields using a Base Entity
We’ll add the DateCreated, UserCreated, DateModified and UserModified fields to each entity by creating a BaseEntity.cs class. Each entity that you want to contain these fields should inherit this class.
public class BaseEntity
{
public DateTime? DateCreated { get; set; }
public string UserCreated { get; set; }
public DateTime? DateModified { get; set; }
public string UserModified { get; set; }
}
For example, my Student.cs entity will looks like this:
public class Student : BaseEntity
{
public int Id { get; set; }
public string Name { get; set; }
}
Override SaveChanges in the DbContext
In this step we’ll intercept entites as they are saved and update their created and modified fields automtically. Take a look at my DbContext below:
public class SchoolContext : DbContext
{
public DbSet<Student> Students { get; set; }
public override int SaveChanges()
{
AddTimestamps();
return base.SaveChanges();
}
public override async Task<int> SaveChangesAsync()
{
AddTimestamps();
return await base.SaveChangesAsync();
}
private void AddTimestamps()
{
var entities = ChangeTracker.Entries().Where(x => x.Entity is BaseEntity && (x.State == EntityState.Added || x.State == EntityState.Modified));
var currentUsername = !string.IsNullOrEmpty(System.Web.HttpContext.Current?.User?.Identity?.Name)
? HttpContext.Current.User.Identity.Name
: "Anonymous";
foreach (var entity in entities)
{
if (entity.State == EntityState.Added)
{
((BaseEntity)entity.Entity).DateCreated = DateTime.UtcNow;
((BaseEntity)entity.Entity).UserCreated = currentUsername;
}
((BaseEntity)entity.Entity).DateModified = DateTime.UtcNow;
((BaseEntity)entity.Entity).UserModified = currentUsername;
}
}
}
Please Note: To track the currently logged in user, you’ll need a reference to the System.Web assembly.
That’s all you need. Now everytime you call SaveChanges the Created and Modified fields will automatically update.