Linq和EntityFramework 4與多個內部連接嵌套子查詢

Question

我想寫在這個產品表上的Linq查詢基於FacetTypes需要按他們的方面分組。

這是表結構：

我獲得通過facetTypeIds的陣列，說9，6，52

FacetTypeId 9 has a name of "160" and is a Facet of "Size"  
FacetTypeId 6 has a name of "157" and is a Facet of "Size"  
FacetTypeId 52 has a name of "Cool Brand" and is a Facet of "Brand" 

他們需要構建成聯接基礎上查詢面，像這樣：

select * from products p 
inner join (select productId from productFacets where facetTypeId in (9, 6)) 
    p1 on p1.productId = p.productId 
inner join (select productId from productFacets where facetTypeId in (52)) 
    p2 on p2.productId = p.productId 

結果是一個結果集，上面寫着：

Get me產品有品牌「酷品牌」和尺寸（160或157）

我將如何去創建一個linq查詢，將動態構建這？

我有點卡在這將如何形成linq。

編輯：

這是代碼，我有點想出但是感覺非常低效。

MyDbContext _context; 

// Groups FacetTypeIds by Facet into int lists 
Dictionary<int, List<int>> createFacetGroup(int[] facetTypeIds) 
{ 
    var facets = new Dictionary<int, List<int>>(); 

    var facetTypes = from ft in _context.FacetTypes where facetTypeIds.Contains(ft.FacetTypeId) select ft; 
    foreach (var facetType in facetTypes) 
    { 
     if (facets.ContainsKey(facetType.Facet.FacetId)) 
      facets[facetType.Facet.FacetId].Add(facetType.FacetTypeId); 
     else 
      facets.Add(facetType.Facet.FacetId, new List<int> { facetType.FacetTypeId }); 
    } 

    return facets; 
} 

public List<Product> FindProductsByGroupedFacetTypeIds(int[] facetTypeIds) 
{ 
    var groupedFacetTypeIds = createFacetGroup(facetTypeIds); 

    // this seem very inefficient but ToList needs to be called 
    // otherwise the results products in the foreach loop dont end 
    // up with the correct result set 
    var products = _context.Products.ToList(); 

    foreach (var facetTypeIdGroup in groupedFacetTypeIds) 
    { 
     var facetTypeIdGroupArray = facetTypeIdGroup.Value.ToArray(); 
     products = (from p in products where p.FacetTypes.Any(x => facetTypeIdGroupArray.Contains(x.FacetTypeId)) select p).ToList(); 
    } 

    return products; 
} 

Answer 1

在結束這個問題的興趣，我會提出我的解決方案這一點。

這不是很漂亮，但它的工作原理。如果任何人有一個更好的解決方案，我很樂意看到它

MyDbContext _context; 

// Groups FacetTypeIds by Facet into int lists 
Dictionary<int, List<int>> createFacetGroup(int[] facetTypeIds) 
{ 
    var facets = new Dictionary<int, List<int>>(); 

    var facetTypes = from ft in _context.FacetTypes where facetTypeIds.Contains(ft.FacetTypeId) select ft; 
    foreach (var facetType in facetTypes) 
    { 
     if (facets.ContainsKey(facetType.Facet.FacetId)) 
      facets[facetType.Facet.FacetId].Add(facetType.FacetTypeId); 
     else 
      facets.Add(facetType.Facet.FacetId, new List<int> { facetType.FacetTypeId }); 
    } 

    return facets; 
} 

public List<Product> FindProductsByGroupedFacetTypeIds(int[] facetTypeIds) 
{ 
    var groupedFacetTypeIds = createFacetGroup(facetTypeIds); 

    // this seem very inefficient but ToList needs to be called 
    // otherwise the results products in the foreach loop dont end 
    // up with the correct result set 
    var products = _context.Products.ToList(); 

    foreach (var facetTypeIdGroup in groupedFacetTypeIds) 
    { 
     var facetTypeIdGroupArray = facetTypeIdGroup.Value.ToArray(); 
     products = (from p in products where p.FacetTypes.Any(x => facetTypeIdGroupArray.Contains(x.FacetTypeId)) select p).ToList(); 
    } 

    return products; 
} 

Answer 2

試試這個 如果實體模型的名字是YourEntitie例如：

YourEntitie urEntity = new YourEntitie(); 
List<Products> prdList = (from pro in urEntity.Products.Include("FacetTypes") 
         where (pro.FacetTypes.Where 
            (fac => fac.FacetTypeID == 9 || 
            fac => fac.FacetTypeID == 6).Count() > 0) 
           && (pro.FacetTypes.Where 
             (fac => fac.FacetTypeID == 52).Count() > 0) 
         select pro).ToList();