ASP.NET MVC 通用仓储库

Question

我搜寻了数个小时，并阅读了多篇有关构建通用存储库（GR）的文章。据我所理解，当存在类似代码时，可以使用GR。例如，通过其ID获取表中的单行或整个表。但是，我仍然无法理解如何实现它。

public interface IEntity<T> where T : class{
     IQueryable<T> getAll();
     T GetById(int id);
}

public class Repository<T> where T : IEntity<T>{
     northWindDataContext nwdc = new northWindDataContext();

    public IQueryable<T> getAll()
    {
         //code to retrive the whole table
    }

    public T GetById(int id)
    {
        //code to retrieve a single row (don't know how to do)
    }
}

那么，我想做类似的事情：

Repository<User> rep = new Repository<User>();
IQueryable<User> = rep.getAll<User>; 
User user = rep.GetById(35);

请问有人可以告诉我如何完成这个任务吗？

- Shaokan

Answer 1

这只是一个伪代码，用于创建一个强类型的通用存储库。

public interface IRepository<TEntity> : IDisposable where TEntity : class
{
        IQueryable<TEntity> GetAll { get; }
        IEntity GetById(int id) { get; }
}

public class EntityRepository<TEntity> : IRepository<TEntity> where TEntity : class
{
    private IContext context;
    private IObjectSet<TEntity> objectSet;



private IObjectSet<TEntity> ObjectSet
{
        get
        {
            if (this.objectSet == null)
            {
                var entitySetProperty = this.Context.GetType().GetProperties().Single(p => p.PropertyType.IsGenericType && typeof(IQueryable<>).MakeGenericType(typeof(TEntity)).IsAssignableFrom(p.PropertyType));

                this.objectSet = (IObjectSet<TEntity>)entitySetProperty.GetValue(this.Context, null);
            }

            return this.objectSet;
        }
}

    public IQueryable<TEntity> GetAll
        {
            get
            {
                return this.ObjectSet;
            }
        }
}

然后您可以创建一个特定的存储库接口，比如说

    public interface IUserRepository : IRepository<User>
    {
    // some additional properties specific to User repository
    ...
    }

    public class UserRepository : EntityRepository<User>, IUserRepository
    {
            public UserRepository(IUnitOfWork uow)
                : base(uow)
            {
            }    
    }

我不确定这是否是您要找的内容。如果您正在使用EF，则可以参考以下内容。

- Reee

Answer 2

我一直在按照这里所描述的使用通用存储库。我一直在使用作者的设计来编写代码，它非常有效。下面是我一直在使用的代码：

IRepository

namespace New_Repository_Design.Repositories
{
    using System;
    using System.Collections.Generic;
    using System.Data.SqlClient;
    using System.Linq;
    using System.Linq.Expressions;
    using Specifications;

    public interface IRepository
    {
        /// <summary>
        /// Gets entity by key.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="keyValue">The key value.</param>
        /// <returns></returns>
        TEntity GetByKey<TEntity>(object keyValue) where TEntity : class;

        /// <summary>
        /// Gets the query.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <returns></returns>
        IQueryable<TEntity> GetQuery<TEntity>() where TEntity : class;

        /// <summary>
        /// Gets the query.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="predicate">The predicate.</param>
        /// <returns></returns>
        IQueryable<TEntity> GetQuery<TEntity>(Expression<Func<TEntity, bool>> predicate) where TEntity : class;

        /// <summary>
        /// Gets the query.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        IQueryable<TEntity> GetQuery<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;

        /// <summary>
        /// Gets one entity based on matching criteria
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        TEntity Single<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class;

        /// <summary>
        /// Gets single entity using specification
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        TEntity Single<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;

        /// <summary>
        /// Firsts the specified predicate.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="predicate">The predicate.</param>
        /// <returns></returns>
        TEntity First<TEntity>(Expression<Func<TEntity, bool>> predicate) where TEntity : class;

        /// <summary>
        /// Gets first entity with specification.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        TEntity First<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;

        /// <summary>
        /// Adds the specified entity.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="entity">The entity.</param>
        void Add<TEntity>(TEntity entity) where TEntity : class;

        /// <summary>
        /// Attaches the specified entity.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="entity">The entity.</param>
        void Attach<TEntity>(TEntity entity) where TEntity : class;

        /// <summary>
        /// Deletes the specified entity.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="entity">The entity.</param>
        void Delete<TEntity>(TEntity entity) where TEntity : class;

        /// <summary>
        /// Deletes one or many entities matching the specified criteria
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        void Delete<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class;

        /// <summary>
        /// Deletes entities which satify specificatiion
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        void Delete<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;

        /// <summary>
        /// Updates changes of the existing entity.
        /// The caller must later call SaveChanges() on the repository explicitly to save the entity to database
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="entity">The entity.</param>
        void Update<TEntity>(TEntity entity) where TEntity : class;

        /// <summary>
        /// Finds entities based on provided criteria.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        IEnumerable<TEntity> Find<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;

        /// <summary>
        /// Finds entities based on provided criteria.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        IEnumerable<TEntity> Find<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class;

        /// <summary>
        /// Finds one entity based on provided criteria.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        TEntity FindOne<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;

        /// <summary>
        /// Finds one entity based on provided criteria.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        TEntity FindOne<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class;

        /// <summary>
        /// Gets all.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <returns></returns>
        IEnumerable<TEntity> GetAll<TEntity>() where TEntity : class;

        /// <summary>
        /// Gets a collection of entity with paging support
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="orderBy">The order by.</param>
        /// <param name="pageIndex">Index of the page.</param>
        /// <param name="pageSize">Size of the page.</param>
        /// <param name="sortOrder">The sort order.</param>
        /// <returns></returns>
        IEnumerable<TEntity> Get<TEntity>(Expression<Func<TEntity, string>> orderBy, int pageIndex, int pageSize, SortOrder sortOrder = SortOrder.Ascending) where TEntity : class;

        /// <summary>
        /// Gets a collection of entity base on criteria with paging support
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <param name="orderBy">The order by.</param>
        /// <param name="pageIndex">Index of the page.</param>
        /// <param name="pageSize">Size of the page.</param>
        /// <param name="sortOrder">The sort order.</param>
        /// <returns></returns>
        IEnumerable<TEntity> Get<TEntity>(Expression<Func<TEntity, bool>> criteria, Expression<Func<TEntity, string>> orderBy, int pageIndex, int pageSize, SortOrder sortOrder = SortOrder.Ascending) where TEntity : class;

        /// <summary>
        /// Gets entities which satify specification
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <param name="orderBy">The order by.</param>
        /// <param name="pageIndex">Index of the page.</param>
        /// <param name="pageSize">Size of the page.</param>
        /// <param name="sortOrder">The sort order.</param>
        /// <returns></returns>
        IEnumerable<TEntity> Get<TEntity>(ISpecification<TEntity> criteria, Expression<Func<TEntity, string>> orderBy, int pageIndex, int pageSize, SortOrder sortOrder = SortOrder.Ascending) where TEntity : class;

        /// <summary>
        /// Counts the specified entities.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <returns></returns>
        int Count<TEntity>() where TEntity : class;

        /// <summary>
        /// Counts entities with the specified criteria.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        int Count<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class;

        /// <summary>
        /// Counts entities satifying specification.
        /// </summary>
        /// <typeparam name="TEntity">The type of the entity.</typeparam>
        /// <param name="criteria">The criteria.</param>
        /// <returns></returns>
        int Count<TEntity>(ISpecification<TEntity> criteria) where TEntity : class;
    }
}

域名仓库

namespace New_Repository_Design.Repositories
{
    using System;
    using System.Collections.Generic;
    using System.Data;
    using System.Data.Entity.Design.PluralizationServices;
    using System.Data.Objects;
    using System.Data.SqlClient;
    using System.Globalization;
    using System.Linq;
    using System.Linq.Expressions;
    using Specifications;

    public sealed class DomainRepository : IRepository
    {
        private readonly PluralizationService _pluralizer = PluralizationService.CreateService(CultureInfo.GetCultureInfo("en"));

        private readonly string _connectionStringName;
        private ObjectContext _objectContext;

        /// <summary>
        /// Initializes a new instance of the <see cref="GenericRepository&lt;TEntity&gt;"/> class.
        /// </summary>
        public DomainRepository()
            : this(string.Empty)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="GenericRepository&lt;TEntity&gt;"/> class.
        /// </summary>
        /// <param name="connectionStringName">Name of the connection string.</param>
        public DomainRepository(string connectionStringName)
        {
            this._connectionStringName = connectionStringName;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="GenericRepository"/> class.
        /// </summary>
        /// <param name="objectContext">The object context.</param>
        public DomainRepository(ObjectContext objectContext)
        {
            if (objectContext == null)
                throw new ArgumentNullException("objectContext");
            this._objectContext = objectContext;
        }

        public TEntity GetByKey<TEntity>(object keyValue) where TEntity : class
        {
            EntityKey key = GetEntityKey<TEntity>(keyValue);

            object originalItem;
            if (ObjectContext.TryGetObjectByKey(key, out originalItem))
            {
                return (TEntity)originalItem;
            }
            return default(TEntity);
        }

        public IQueryable<TEntity> GetQuery<TEntity>() where TEntity : class
        {
            var entityName = GetEntityName<TEntity>();
            var q = ObjectContext.CreateQuery<TEntity>(entityName);
            //return ObjectContext.CreateQuery<TEntity>(entityName);
            return q;
        }

        public IQueryable<TEntity> GetQuery<TEntity>(Expression<Func<TEntity, bool>> predicate) where TEntity : class
        {
            return GetQuery<TEntity>().Where(predicate);
        }

        public IQueryable<TEntity> GetQuery<TEntity>(ISpecification<TEntity> specification) where TEntity : class
        {
            return specification.SatisfyingEntitiesFrom(GetQuery<TEntity>());
        }

        public IEnumerable<TEntity> Get<TEntity>(Expression<Func<TEntity, string>> orderBy, int pageIndex, int pageSize, SortOrder sortOrder = SortOrder.Ascending) where TEntity : class
        {
            if (sortOrder == SortOrder.Ascending)
            {
                return GetQuery<TEntity>().OrderBy(orderBy).Skip(pageIndex).Take(pageSize).AsEnumerable();
            }
            return GetQuery<TEntity>().OrderByDescending(orderBy).Skip(pageIndex).Take(pageSize).AsEnumerable();
        }

        public IEnumerable<TEntity> Get<TEntity>(Expression<Func<TEntity, bool>> predicate, Expression<Func<TEntity, string>> orderBy, int pageIndex, int pageSize, SortOrder sortOrder = SortOrder.Ascending) where TEntity : class
        {
            if (sortOrder == SortOrder.Ascending)
            {
                return GetQuery<TEntity>().Where(predicate).OrderBy(orderBy).Skip(pageIndex).Take(pageSize).AsEnumerable();
            }
            return GetQuery<TEntity>().Where(predicate).OrderByDescending(orderBy).Skip(pageIndex).Take(pageSize).AsEnumerable();
        }

        public IEnumerable<TEntity> Get<TEntity>(ISpecification<TEntity> specification, Expression<Func<TEntity, string>> orderBy, int pageIndex, int pageSize, SortOrder sortOrder = SortOrder.Ascending) where TEntity : class
        {
            if (sortOrder == SortOrder.Ascending)
            {
                return specification.SatisfyingEntitiesFrom(GetQuery<TEntity>()).OrderBy(orderBy).Skip(pageIndex).Take(pageSize).AsEnumerable();
            }
            return specification.SatisfyingEntitiesFrom(GetQuery<TEntity>()).OrderByDescending(orderBy).Skip(pageIndex).Take(pageSize).AsEnumerable();
        }

        public TEntity Single<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class
        {
            return GetQuery<TEntity>().SingleOrDefault<TEntity>(criteria);
        }

        public TEntity Single<TEntity>(ISpecification<TEntity> criteria) where TEntity : class
        {
            return criteria.SatisfyingEntityFrom(GetQuery<TEntity>());
        }

        public TEntity First<TEntity>(Expression<Func<TEntity, bool>> predicate) where TEntity : class
        {
            return GetQuery<TEntity>().FirstOrDefault(predicate);
        }

        public TEntity First<TEntity>(ISpecification<TEntity> criteria) where TEntity : class
        {
            return criteria.SatisfyingEntitiesFrom(GetQuery<TEntity>()).FirstOrDefault();
        }

        public void Add<TEntity>(TEntity entity) where TEntity : class
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }
            ObjectContext.AddObject(GetEntityName<TEntity>(), entity);
        }

        public void Attach<TEntity>(TEntity entity) where TEntity : class
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }

            ObjectContext.AttachTo(GetEntityName<TEntity>(), entity);
        }

        public void SaveChanges()
        {
            this.ObjectContext.SaveChanges();
        }

        public void Delete<TEntity>(TEntity entity) where TEntity : class
        {
            if (entity == null)
            {
                throw new ArgumentNullException("entity");
            }
            ObjectContext.DeleteObject(entity);
        }

        public void Delete<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class
        {
            IEnumerable<TEntity> records = Find<TEntity>(criteria);

            foreach (TEntity record in records)
            {
                Delete<TEntity>(record);
            }
        }

        public void Delete<TEntity>(ISpecification<TEntity> criteria) where TEntity : class
        {
            IEnumerable<TEntity> records = Find<TEntity>(criteria);
            foreach (TEntity record in records)
            {
                Delete<TEntity>(record);
            }
        }

        public IEnumerable<TEntity> GetAll<TEntity>() where TEntity : class
        {
            return GetQuery<TEntity>().AsEnumerable();
        }

        public void Update<TEntity>(TEntity entity) where TEntity : class
        {
            var fqen = GetEntityName<TEntity>();

            object originalItem;
            EntityKey key = ObjectContext.CreateEntityKey(fqen, entity);
            if (ObjectContext.TryGetObjectByKey(key, out originalItem))
            {
                ObjectContext.ApplyCurrentValues(key.EntitySetName, entity);
            }
        }

        public IEnumerable<TEntity> Find<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class
        {
            return GetQuery<TEntity>().Where(criteria);
        }

        public TEntity FindOne<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class
        {
            return GetQuery<TEntity>().Where(criteria).FirstOrDefault();
        }

        public TEntity FindOne<TEntity>(ISpecification<TEntity> criteria) where TEntity : class
        {
            return criteria.SatisfyingEntityFrom(GetQuery<TEntity>());
        }

        public IEnumerable<TEntity> Find<TEntity>(ISpecification<TEntity> criteria) where TEntity : class
        {
            return criteria.SatisfyingEntitiesFrom(GetQuery<TEntity>());
        }

        public int Count<TEntity>() where TEntity : class
        {
            return GetQuery<TEntity>().Count();
        }

        public int Count<TEntity>(Expression<Func<TEntity, bool>> criteria) where TEntity : class
        {
            return GetQuery<TEntity>().Count(criteria);
        }

        public int Count<TEntity>(ISpecification<TEntity> criteria) where TEntity : class
        {
            return criteria.SatisfyingEntitiesFrom(GetQuery<TEntity>()).Count();
        }

        private ObjectContext ObjectContext
        {
            get
            {
                return this._objectContext;
            }
        }

        private string GetEntityName<TEntity>() where TEntity : class
        {
            return string.Format("{0}.{1}", ObjectContext.DefaultContainerName, _pluralizer.Pluralize(typeof(TEntity).Name));
        }

        private EntityKey GetEntityKey<TEntity>(object keyValue) where TEntity : class
        {
            var entitySetName = GetEntityName<TEntity>();
            var objectSet = ObjectContext.CreateObjectSet<TEntity>();
            var keyPropertyName = objectSet.EntitySet.ElementType.KeyMembers[0].ToString();
            var entityKey = new EntityKey(entitySetName, new[] { new EntityKeyMember(keyPropertyName, keyValue) });
            return entityKey;
        }
    }
}`

例如，通过ID获取项目。 DomainRepository.FindOne<User>(u => u.Id == userId); 将返回单个用户。或者 DomainRepository.Find<User>(u => u.UserName.Contains("Blah")); 试用这个存储库，看看它是否适合您的需求。

- Jason Evans