如何通过Linq在一对多关系上筛选查询

Question

我有一个产品和一个零件表。这是该协会：

Create Table Product 
{ 
    Id int, 
    Name nvarchar(max) 
} 

Create Table Part 
{ 
    Id int, 
    Name nvarchar (max), 
    ProductID int (foreign key to Product.Id), 
    SomeCategoryId int 
} 

现在，我想回到产品的列表，零部件只包括200

规则，SomeCategoryId的列表：

• 如果一个Part.SomeCategoryId <> 200，不包括零件
• 如果没有Part.SomeCategoryId == 200对应于产品通过Part.Product.Id，删除整个产品。

如何让我的代码更高效？

prods = db.Products.OrderBy(o => o.Name).Select(pr => new ProductViewModel 
{ 
    Id = pr.Id, 
    Name = pr.Name, 
    Parts = pr.Parts.OrderBy(o => o.Name).Select(prt => new PartViewModel 
    { 
     Id = prt.Id, 
     Name = prt.Name, 
     SomeCategoryId = prt.SomeCategoryId 
    }).Where(w => w.SomeCategoryId == 200).ToList() 
}).ToList(); 

foreach(var prod in prods) 
{ 
    var isSomeCategory = false; 
    foreach (var part in prod.Parts) 
    { 
     if (part.SomeCategoryId == 200) 
     { 
      isSomeCategory = !isSomeCategory; 
     } 
    } 

    if (isSomeCategory == false) 
    { 
     prods.Remove(prod); 
    } 
} 

Answer 1

怎么样......

prods = db.Products.Where(pr => pr.Parts.Any(p => p.SomeCategoryId == 200)).OrderBy(o => o.Name).Select(pr => new ProductViewModel 
{ 
    Id = pr.Id, 
    Name = pr.Name, 
    Parts = pr.Parts.OrderBy(o => o.Name).Select(prt => new PartViewModel 
    { 
     Id = prt.Id, 
     Name = prt.Name, 
     SomeCategoryId = prt.SomeCategoryId 
    }).Where(w => w.SomeCategoryId == 200).ToList() 
}).ToList();