I have a repository abstract class that encapsulates pretty much all of the CRUD functionality:
public abstract class DataRepository<T> : IRepository<T>
where T : class
{
public DataContext Context { get; private set; }
public TransactionScope Transaction { get; private set; }
/// <summary>
/// A <see cref="bool"/> function that compares the keys for fetching a single item, for example:
/// return item1.Id == item2.Id (as an anonymous delegate).
/// </summary>
public Func<T, T, bool> KeyCompare { get; private set; }
/// <summary>
/// Creates a new data repository.
/// </summary>
/// <param name="context"></param>
/// <param name="scope"></param>
/// <param name="keyCompare">
/// A <see cref="bool"/> function that compares the keys for fetching a single item, for example:
/// return item1.Id == item2.Id (as an anonymous delegate).
/// </param>
public DataRepository(DataContext context, TransactionScope scope, Func<T, T, bool> keyCompare)
{
Context = context;
Transaction = scope;
KeyCompare = keyCompare;
}
public virtual T Item(T item)
{
return Items().SingleOrDefault(e => KeyCompare(e, item));
}
public virtual IEnumerable<T> Items()
{
return DataTable.AsEnumerable();
}
protected virtual Table<T> DataTable { get { return Context.GetTable<T>(); } }
/// <summary>
/// A method that updates the non-key fields of an existing entity with those of specified <see cref="item"/>.
/// Called by the <see cref="Save"/> method.
/// </summary>
/// <param name="existing">The existing record to update.</param>
/// <param name="item">A <see cref="T"/> object containing the values to update <see cref="existing"/> object with.</param>
/// <returns></returns>
protected abstract void UpdateExisting(T existing, T item);
/// <summary>
/// A method that updates an existing item or creates a new one, as needed.
/// </summary>
/// <param name="item">The entity containing the values to be saved.</param>
public virtual void Save(T item)
{
var existing = Item(item);
if (existing != null)
{
UpdateExisting(existing, item);
}
else
{
DataTable.InsertOnSubmit(item);
}
Context.SubmitChanges();
}
/// <summary>
/// A method that saves all specified items (creates new, updates existing).
/// </summary>
/// <param name="items">The entities to be saved.</param>
public virtual void Save(IEnumerable<T> items)
{
foreach (var item in items)
{
Save(item);
}
}
/// <summary>
/// A method that deletes specified item.
/// </summary>
/// <param name="item"></param>
public virtual void Delete(T item)
{
var existing = Item(item);
if (existing != null)
{
DataTable.DeleteOnSubmit(existing);
}
Context.SubmitChanges();
}
public virtual void Delete(IEnumerable<T> items)
{
var selection = Items().Where(e => items.Any(item => KeyCompare(e, item)));
DataTable.DeleteAllOnSubmit(selection);
Context.SubmitChanges();
}
}
The KeyCompare property is used like this in the derived classes, so that the base class knows how to isolate a single item in the repository (not all "entities" have a "Id" property, and some keys span multiple columns - this solution attempts to resolve that particular point):
public AuthInfoRepository(DataContext context, TransactionScope scope)
: base(context, scope, (item1, item2) => { return item1.Id == item2.Id;})
{ }
This KeyCompare property is really the cornerstone that allows the derived classes to merely implement the UpdateExisting method, like this:
protected override void UpdateExisting(AuthInfo existing, AuthInfo item)
{
existing.AuthId = item.AuthId;
existing.ActiveDirectoryGroup = item.ActiveDirectoryGroup;
}
The rest (actual CRUD) is all handled by the base class. With this abstract repository I have been implementing the concrete ones in minutes if not seconds, writing only the code that is specific to each implementation. So DRY I'm thirsty.
The DataRepository<T> deals with SQL Server, so I needed yet another implementation for mocking, which I've called ListRepository<T> and does pretty much exactly the same thing (except Context and Transaction properties both return null). I think the constructor's signature is all I need to post here:
public ListRepository(IEnumerable<T> items, Func<T, T, bool> keyCompare)
So now I'd be ready for testing, and I want to use Ninject as my IoC container. My problem is that I can't seem to figure out how to pass an anonymous delegate as a ConstructorArgument:
Bind<IRepository<AuthInfo>>().To<ListRepository<AuthInfo>>()
.WithConstructorArgument("items", _mockAuthInfo)
.WithConstructorArgument("keyCompare", ??????);
Is what I'm trying to do feasible, or just over-complicated? I'm not going to ask if it's good/clean code, but constructive comments are welcome over here:
