DBSet.Find() API missing in Entity Framework Core Final RC1 Version

Recently, I was writing the infrastructure part of My Movie Review SPA app using ASP.NET Core version. Then, I landed in a really weird situation where in DBSet.Find() a piece is missing. This is a really crucial extension method for finding the record based on the primary key. In order to find the solution, I thought it would be nice to talk to EF Guru Julie Lerman directly. Here is what I asked her and what she replied on the same.

 

Here, at this point I got the confirmation, this feature is yet to be included by EF Team. Hence, I decided to use the interim solution provided by the EF Team themselves. Below is the extension method which I have written to serve the same result.

using System;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.Data.Entity;
using Microsoft.Data.Entity.Infrastructure;

namespace MovieReviewSPA.Data.Helpers
{
    public static class Extensions
    {
        public static TEntity Find<TEntity>(this DbSet<TEntity> set, params object[] keyValues) where TEntity : class
        {
            var context = ((IInfrastructure<IServiceProvider>)set).GetService<DbContext>();

            var entityType = context.Model.FindEntityType(typeof(TEntity));
            var key = entityType.FindPrimaryKey();

            var entries = context.ChangeTracker.Entries<TEntity>();

            var i = 0;
            foreach (var property in key.Properties)
            {
                entries = Enumerable.Where(entries, e => e.Property(property.Name).CurrentValue == keyValues[i]);
                i++;
            }

            var entry = entries.FirstOrDefault();
            if (entry != null)
            {
                // Return the local object if it exists.
                return entry.Entity;
            }

            // TODO: Build the real LINQ Expression
            // set.Where(x => x.Id == keyValues[0]);
            var parameter = Expression.Parameter(typeof(TEntity), "x");
            var query = Queryable.Where(set, (Expression<Func<TEntity, bool>>)
                Expression.Lambda(
                    Expression.Equal(
                        Expression.Property(parameter, "Id"),
                        Expression.Constant(keyValues[0])),
                    parameter));

            // Look in the database
            return query.FirstOrDefault();
        }
    }
}

And, here is the completed Repository Pattern for my project.

using System;
using System.Linq;
using Microsoft.Data.Entity;
using Microsoft.Data.Entity.ChangeTracking;
using MovieReviewSPA.Data.Contracts;
using MovieReviewSPA.Data.Helpers;
using DbContext = Microsoft.Data.Entity.DbContext;
using EntityState = Microsoft.Data.Entity.EntityState;

namespace MovieReviewSPA.Data
{
    public class EFRepository<T> : IRepository<T> where T : class
    {
        public EFRepository(DbContext dbContext)
        {
            if (dbContext == null)
                throw new ArgumentNullException("dbContext");
            DbContext = dbContext;
            DbSet = DbContext.Set<T>();
        }

        protected DbContext DbContext { get; set; }
        protected DbSet<T> DbSet { get; set; }
        public virtual IQueryable<T> GetAll()
        {
            return DbSet;
        }

        public virtual T GetById(int id)
        {
            //EF Core Will be updated shortly with Find Extension by Default
            //Here, I have written Extension method for the same
            //Source:- http://stackoverflow.com/questions/29030472/dbset-doesnt-have-a-find-method-in-ef7/29082410#29082410
            return DbSet.Find(id);
        }

        public virtual void Add(T entity)
        {
            EntityEntry<T> dbEntityEntry = DbContext.Entry(entity);
            if (dbEntityEntry.State != (EntityState) EntityState.Detached)
            {
                dbEntityEntry.State = EntityState.Added;
            }
            else
            {
                DbSet.Add(entity);
            }
        }

        public virtual void Update(T entity)
        {
            EntityEntry<T> dbEntityEntry = DbContext.Entry(entity);
            if (dbEntityEntry.State != (EntityState) EntityState.Detached)
            {
                DbSet.Attach(entity);
            }
            dbEntityEntry.State = EntityState.Modified;
        }

        public void Delete(T entity)
        {
            EntityEntry<T> dbEntityEntry = DbContext.Entry(entity);
            if (dbEntityEntry.State != (EntityState) EntityState.Deleted)
            {
                dbEntityEntry.State = EntityState.Deleted;
            }
            else
            {
                DbSet.Attach(entity);
                DbSet.Remove(entity);
            }
        }

        public void Delete(int id)
        {
            var entity = GetById(id);
            if (entity == null) return;

            Delete(entity);
        }
    }

}

Now, below is the glimpse of the solution structure so far for my Movie Review SPA coming up using ASP.NET Core, WEB-API, Angular JS, Entity Framework and tons of new things.



I hope you  have liked this discussion. Thanks for joining me.