Question

I want to implement Repository Pattern in my ASP.NET MVC + EF 4.3 project.

Right now my DBContext class has an override to SaveChanges that receives a “userid” parameter in order to do Audit Trail.

Example:

  // 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();
            }

Now, my RepositoryBase class has something like this:

 public class RepositoryBase<C> : IDisposable
        where C : DbContext, new()
    {
        private C _DataContext;

        public virtual C DataContext
        {
            get
            {
                if (_DataContext == null)
                {
                    _DataContext = new C();
                    this.AllowSerialization = true;
                    //Disable ProxyCreationDisabled to prevent the "In order to serialize the parameter, add the type to the known types collection for the operation using ServiceKnownTypeAttribute" error
                }
                return _DataContext;
            }
        }

My question is how can I expose the SaveChanges(int) method inside my RepositoryBase class?

Any clue?

Answer 1

You’re going to need to use your actual DbContext in your generic definition instead of DbContext base class. Then you’ll be able to call your overridden function

 public class RepositoryBase<C> : IDisposable
        where C : YourContextClassGoesHere, new()

{
    private C _dataContext;

    public void SaveChanges()
    {
        int userId = GetUserId();
       _dataContext.SaveChanges(userId);
    }
}