What is extension for DbSet? I want to add method 'FindTheLatest'. this is my code: this is my code
public static List FindTheLatest(this DbSet<Review> reviews, int nums) { return reviews.OrderByDescending(r => r.Created).Take(nums).ToList(); }
But it doesn't work. What i must to do?
this is my extension class:
public static class RestaurantReviewsExtenstion
{
public static IEnumerable<Review> FindTheLatest(this IQueryable<Review> reviews, int nums)
{
return reviews.OrderByDescending(r => r.Created).Take(nums).ToList();
}
public static Review FindById(this System.Data.Entity.DbSet<Review> reviews, int id)
{
return reviews.SingleOrDefault(s => s.ReviewId == id);
//return reviews.Find(item => item.Id == id);
}
public static Review FindTheBest(this List<Review> list)
{
return list.OrderByDescending(o => o.Rating).FirstOrDefault();
}
}
this is my DBContex Class:
public class OdeToFoodDb: DbContext
{
public DbSet<Restaurant> Restaurants { get; set; }
public DbSet<Review> Reviews { get; set; }
protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Restaurant>()
.HasMany(resturant => resturant.Reviews)
.WithRequired(review => review.Resturant);
base.OnModelCreating(modelBuilder);
}
}
this is where i get error:
OdeToFoodDb _db = new OdeToFoodDb();
public PartialViewResult LatestReview()
{
System.Threading.Thread.Sleep(1500);
//this is where i get error
var review = _db.Reviews.FindTheLatest(1);
//************************************
return PartialView("_Review", review);
}
Sorry about poor information.
Well for one thing, List
is a generic type. For another DbSet
isn't a set of any specific type - you probably want DbSet<T>
for some appropriate T
. Perhaps you mean:
public static List<Review> FindTheLatest(this DbSet<Review> reviews, int nums)
{
return reviews.OrderByDescending(r => r.Created).Take(nums).ToList();
}
Or:
public static List<Review> FindTheLatest(this DbSet reviews, int nums)
{
return reviews.Cast<Review>()
.OrderByDescending(r => r.Created)
.Take(nums)
.ToList();
}
you can implement extension method using Generic to accept any type:
public static class DbSetExtensions
{
public static IQueryable<T> FindTheLast<T,TResult>(this IQueryable<T> t, Expression<Func<T, TResult>> expression, int nums) where T : class
{
return t.OrderByDescending(expression).Take(nums);
}
}
and use it :
dbContext.Entity.FindTheLast(x => x.Property,2);
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