IQueryable不返回Count属性

Question

    public interface IRepository<T> : IDisposable
    {
        void Add(T newEntity);
        void Delete(T entity);
        T Find(int id);
        IQueryable<T> FindAll();
        int Commit();
    }

  public class SqlRepository<T> : IRepository<T> where T : class
    {
        DbContext context;
        DbSet<T> set;
        public SqlRepository(DbContext context)
        {
            this.context = context;
            this.set = context.Set<T>();
        }

        public void Add(T newEntity)
        {
            this.set.Add(newEntity);
        }

        public void Delete(T entity)
        {

        }

        public T Find(int id)
        {
            throw new Exception("todo");
        }

        public IQueryable<T> FindAll()
        {
            return this.set;
        }

        public int Commit()
        {
            return this.context.SaveChanges();
        }

        public void Dispose()
        {
            this.context.Dispose();
        }
    }


    using (IRepository<Contact> e = new SqlRepository<Contact>(new AppointmentReminderDb()))
    {
        e.Add(new Contact() { Active = true });
        e.Add(new Contact() { Active = true });
        e.Commit();
        var count = await e.FindAll().Count(); // do not get Count property
    }

In the above line of code, I don't understand why I am not getting Count property. Instead I get CountAsynch. I really want to simply get Count property. My IQueryable for FindAll is correctly defined in the interface and in the class method.

Answer 1

You may have forgotten to include the right namespace.

The method you're seeing in IntelliSense is named QueryableExtensions.CountAsync<TSource> defined in the System.Data.Entity namespace, which returns Task<int> and, as such, should be awaited.

The method (not property ) you're looking for is named Queryable.Count<T>() and is defined in the System.Linq namespace. It returns an int and should not be awaited.

If the operation involves IO, which it probably does, you want to use CountAsync .