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Generic Repository with Entity Framework Core

Recently I worked on a project with ASP.NET Core which uses Entity Framework Core.
With them, I used a generic repository pattern in the data layer.
Repository interface was like below:
 using System;  
 using System.Collections.Generic;  
 using System.Linq.Expressions;  
 using OnlineSurvey.Models;  
 namespace OnlineSurvey.Data  
 {  
   public interface IRepository<T> where T : BaseEntity  
   {  
     T GetById(int id, params Expression<Func<T, object>>[] includExpressions);  
     void Add(T entity);  
     void Delete(T entity);  
     void Delete(int id);  
     IEnumerable<T> GetAll(params Expression<Func<T, object>>[] includExpressions);  
     IEnumerable<T> Find(Expression<Func<T, bool>> where);  
     int Count();  
   }  
 }
And the implementation was like below: 
 using System;  
 using System.Data.Entity;  
 using System.Data.Entity.Infrastructure;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Linq.Expressions;  
 using OnlineSurvey.Models;  
 namespace OnlineSurvey.Data  
 {  
   public class Repository<T> : IRepository<T> where T : BaseEntity  
   {  
     protected DbSet<T> DbSet => this.Context.Set<T>();  
     protected DataContext Context { get; set; }  
     public Repository(DataContext context)  
     {  
       this.Context = context ?? throw new ArgumentException("An instance of DbContext is required to use this repository.", nameof(context));  
     }  
     public IEnumerable<T> GetAll(params Expression<Func<T, object>>[] includExpressions)  
     {  
       if (includExpressions.Any())  
       {  
         return  
           includExpressions.Aggregate<Expression<Func<T, object>>, IQueryable<T>>(this.DbSet,  
             (current, expression) => current.Include(expression)).ToList();  
       }  
       return this.DbSet.ToList();  
     }  
     public T GetById(int id, params Expression<Func<T, object>>[] includExpressions)  
     {  
       if (includExpressions.Any())  
       {  
         var set =  
           includExpressions.Aggregate<Expression<Func<T, object>>, IQueryable<T>>(this.DbSet,  
             (current, expression) => current.Include(expression));  
         return set.SingleOrDefault(s => s.Id == id);  
       }  
       return this.DbSet.Find(id);  
     }  
     public void Add(T entity)  
     {  
       DbEntityEntry entry = this.Context.Entry(entity);  
       if (entry.State != EntityState.Detached)  
       {  
         entry.State = EntityState.Added;  
       }  
       else  
       {  
         this.DbSet.Add(entity);  
       }  
     }  
     public void Delete(T entity)  
     {  
       DbEntityEntry entry = this.Context.Entry(entity);  
       if (entry.State != EntityState.Deleted)  
       {  
         entry.State = EntityState.Deleted;  
       }  
       else  
       {  
         this.DbSet.Attach(entity);  
         this.DbSet.Remove(entity);  
       }  
     }  
     public void Delete(int id)  
     {  
       var entity = this.GetById(id);  
       if (entity != null)  
       {  
         this.Delete(entity);  
       }  
     }  
     public IEnumerable<T> Find(Expression<Func<T, bool>> where)  
     {  
       return DbSet.Where(where).ToList();  
     }  
     public int Count()  
     {  
       return DbSet.Count();  
     }  
   }  
 }

Usage of the above mentioned implementation:
 Question question = this._unitOfWork.Questions.GetById(id, q=>q.Answers);
Above code has one issue. There is no way load entities inside a list. This problem can be fixed if we could have access to inbuilt function .ThenInclude.

 The following change will give us access to the above mentioned function.
 using System;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Linq.Expressions;  
 using System.Threading.Tasks;  
 using OnlineSurvey.Models;  
 using Microsoft.EntityFrameworkCore.Query;
  
 namespace OnlineSurvey.Data  
 {  
   public interface IRepository<T> where T : BaseEntity  
   {  
     Task<T> GetByIdAsync(int id, Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null);  
     Task AddAsync(T entity);  
     void Delete(T entity);  
     Task DeleteAsync(int id);  
     Task<IEnumerable<T>> GetAllAsync(Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null);  
     Task<IEnumerable<T>> FindAsync(Expression<Func<T, bool>> predicate = null,  
                     Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null);  
     int Count();  
     Task<T> FirstOrDefaultAsync(Expression<Func<T, bool>> predicte = null,  
                   Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null);  
     void Update(T entity);  
   }  
 }
Refer to the below implementation:
 using System;  
 using System.Data.Entity;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Linq.Expressions;  
 using OnlineSurvey.Models;  
 using System.Threading.Tasks;  
 namespace OnlineSurvey.Data  
 {  
   public class Repository<T> : IRepository<T> where T : BaseEntity  
   {  
     protected DbSet<T> DbSet => this.Context.Set<T>();  
     protected DbContext Context { get; set; }  
     public Repository(DbContext context)  
     {  
       this.Context = context ?? throw new ArgumentException("An instance of DbContext is required to use this repository.", "context");  
     }  
     public async Task<T> GetByIdAsync(int id, Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null)  
     {  
       IQueryable<T> query = this.DbSet;  
       if(include != null)  
       {  
         query = include(query);  
       }  
       return await query.AsNoTracking().SingleOrDefaultAsync(s => s.Id == id);  
     }  
     public async Task AddAsync(T entity)  
     {  
       EntityEntry entry = this.Context.Entry(entity);  
       if(entity.State != EntityState.Detached)  
       {  
         entry.State = EntityState.Added;  
       }  
       else  
       {  
         await this.DbSet.AddAsync(entity);  
       }  
     }  
     public void Delete(T entity)  
     {  
       EntityEntry entry = this.Context.Entry(entity);  
       if (entity.State != EntityState.Deleted)  
       {  
         entry.State = EntityState.Deleted;  
       }  
       else  
       {  
         this.DbSet.Attach(entity);  
         this.DbSet.Remove(entity);  
       }  
     }  
     public async Task DeleteAsync(int id)  
     {  
       T entity = await this.GetByIdAsync(id);  
       if(entity != null)  
       {  
         this.Delete(entity);  
       }  
     }  
     public async Task<IEnumerable<T>> GetAllAsync(Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null)  
     {  
       IQueryable<T> query = this.DbSet;  
       if (include != null)  
       {  
         query = include(query);  
       }  
       return await query.AsNoTracking().ToListAsync();  
     }  
     public async Task<IEnumerable<T>> FindAsync(Expression<Func<T, bool>> predicate = null, Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null)  
     {  
       IQueryable<T> query = this.DbSet;  
       if (include != null)  
       {  
         query = include(query);  
       }  
       if(predicate != null)  
       {  
         query = query.Where(predicate);  
       }  
       return await query.AsNoTracking().ToListAsync();  
     }  
     public int Count()  
     {  
       return this.DbSet.Count();  
     }  
     public async Task<T> FirstOrDefaultAsync(Expression<Func<T, bool>> predicate = null, Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null)  
     {  
       IQueryable<T> query = this.DbSet;  
       if (include != null)  
       {  
         query = include(query);  
       }  
       if (predicate != null)  
       {  
         query = query.Where(predicate);  
       }  
       return await query.FirstOrDefaultAsync();  
     }  
     public void Update(T entity)  
     {  
       EntityEntry entry = this.Context.Entry(entity);  
       entity.State = EntityState.Modified;  
     }  
   }  
 }
Usage of the above-mentioned implementation:
 Question question = this._unitOfWork.Questions.GetById(id, q=>q.Include(q => q.Answers).ThenInclude(a => a.Question));
Hope this helps you in some way.
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