首先使用實體​​框架代碼實現存儲庫的通用方法

Question

我正在使用Entity Framework 4.1和repository pattern。

我正在嘗試創建將在大多數場景中使用的方法。我正在嘗試創建一個方法，根據提供的順序標準將記錄歸併並對其進行排序。它可以按1,2或3列進行排序。我希望這個被指定。我在Orchard framework中發現了以下代碼。

在他們下面的IRepository interface（我離開了其他方法）：

public interface IRepository<T> 
{ 
    IEnumerable<T> Fetch(Expression<Func<T, bool>> predicate); 
    IEnumerable<T> Fetch(Expression<Func<T, bool>> predicate, Action<Orderable<T>> order); 
} 

爲IEnumerable<T> Fetch(Expression<Func<T, bool>> predicate, Action<Orderable<T>> order);的實現是：

public class Repository<T> : IRepository<T> 
{ 
    public virtual IQueryable<T> Fetch(Expression<Func<T, bool>> predicate) 
    { 
      return Table.Where(predicate); 
    } 

    public virtual IQueryable<T> Fetch(Expression<Func<T, bool>> predicate, Action<Orderable<T>> order) 
    { 
      var orderable = new Orderable<T>(Fetch(predicate)); 
      order(orderable); 
      return orderable.Queryable; 
    } 
} 

的Orderable class：

public class Orderable<T> 
{ 
    private IQueryable<T> _queryable; 

    public Orderable(IQueryable<T> enumerable) 
    { 
      _queryable = enumerable; 
    } 

    public IQueryable<T> Queryable 
    { 
      get { return _queryable; } 
    } 

    public Orderable<T> Asc<TKey>(Expression<Func<T, TKey>> keySelector) 
    { 
      _queryable = _queryable 
       .OrderBy(keySelector); 
      return this; 
    } 

    public Orderable<T> Asc<TKey1, TKey2>(Expression<Func<T, TKey1>> keySelector1, 
      Expression<Func<T, TKey2>> keySelector2) 
    { 
      _queryable = _queryable 
       .OrderBy(keySelector1) 
       .OrderBy(keySelector2); 
      return this; 
    } 

    public Orderable<T> Asc<TKey1, TKey2, TKey3>(Expression<Func<T, TKey1>> keySelector1, 
      Expression<Func<T, TKey2>> keySelector2, 
      Expression<Func<T, TKey3>> keySelector3) 
    { 
      _queryable = _queryable 
       .OrderBy(keySelector1) 
       .OrderBy(keySelector2) 
       .OrderBy(keySelector3); 
      return this; 
    } 

    public Orderable<T> Desc<TKey>(Expression<Func<T, TKey>> keySelector) 
    { 
      _queryable = _queryable 
       .OrderByDescending(keySelector); 
      return this; 
    } 

    public Orderable<T> Desc<TKey1, TKey2>(Expression<Func<T, TKey1>> keySelector1, 
      Expression<Func<T, TKey2>> keySelector2) 
    { 
      _queryable = _queryable 
       .OrderByDescending(keySelector1) 
       .OrderByDescending(keySelector2); 
      return this; 
    } 

    public Orderable<T> Desc<TKey1, TKey2, TKey3>(Expression<Func<T, TKey1>> keySelector1, 
      Expression<Func<T, TKey2>> keySelector2, 
      Expression<Func<T, TKey3>> keySelector3) 
    { 
      _queryable = _queryable 
       .OrderByDescending(keySelector1) 
       .OrderByDescending(keySelector2) 
       .OrderByDescending(keySelector3); 
      return this; 
    } 
} 

所以可以使用這種方法如下：

var foos = _fooRepos.Fetch(
    f => f.Name == "two" || f.Name == "three", 
    o => o.Asc(f => f.Name, f => f.Id) 
); 

這是做我想達到的最好的方式嗎？我試圖儘可能簡單。我將不勝感激所有幫助，如果有任何示例代碼和文章。

Answer 1

我敢肯定，Orchard傢伙有他們的理由（沒有看過代碼庫），但我只是想知道它是什麼帶來了表與一個更標準的基於LINQ/IQueryable的解決方案相比？

public interface IRepository<T> 
{ 
    IQueryable<T> All(); 
} 

用法：

var foos = from f in _foosRepos.All() 
      where f.Name == "two" || f.Name == "three" 
      orderby f.Name, f.Id; 

或

var foos = _foosRepos.All() 
     .Where(f => f.Name == "two" || f.Name == "three") 
     .OrderBy(f => f.Name).ThenBy(f => f.Id); 

Answer 2

既然你提到的項目可以通過1,2或3個字段進行排序，則可以擴大jeroenh的反應，和「合併「它與果園的邏輯：

public interface IRepository<T> 
{ 
    IQueryable<T> All(); 
    IQueryable<T> Sorted(Func<T, object> sort1, Func<T, object> sort2 = null, Func<T, object> sort3 = null); 
} 

public class Repository<T> : IRepository<T> 
{ 
    public IQueryable<T> All() 
    { 
     // TODO: Implement real data retrieval 
     return new List<T>().AsQueryable(); 
    } 

    public IQueryable<T> Sorted(Func<T, object> sort1, Func<T, object> sort2 = null, Func<T, object> sort3 = null) 
    { 
     var list = All(); 

     var res = list.OrderBy(sort1); 
     if (sort2 != null) 
      res = res.ThenBy(sort2); 
     if (sort3 != null) 
      res = res.ThenBy(sort3); 
     return res.AsQueryable(); 
    } 
} 

Answer 3

又見通用存儲庫實現，使您可以在本教程中指定順序標準： http://www.asp.net/entity-framework/tutorials/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application