Linq查询，通过与不直接连接

Question

在EF模型使用这些类两个表涉及做组：

class BoxOutput 
{ 
    public long BoxId { get; set; } 
    public virtual Box Box { get; set; } 
    public long BoxId { get; set; } 
    public long CategoryId { get; set; } 
    public virtual Category Category { get; set; } 
    public long? ColorId { get; set; } 
    public virtual Category Color { get; set; } 
    public decimal Weight { get; set; } 

    // ...and other irrelevant properties 
} 

class BoxInput 
{ 
    public long BoxId { get; set; } 
    public virtual Box Box { get; set; } 
    public long BoxId { get; set; } 
    public long CategoryId { get; set; } 
    public virtual Category Category { get; set; } 
    public long? ColorId { get; set; } 
    public virtual Category Color { get; set; } 
    public decimal Weight { get; set; } 

    // ...and other irrelevant properties 
} 

......我该怎么办LINQ查询，对于一个特定的盒（如boxId = 12），返回此?:

category.name color.name  inputWeightsSum  outputWeightsSum 
--------------------------------------------------------------------------- 
    c    null    0     0 
    c    red    0     0 
    c    blue    0     0 
    m    null    0     0 
    m    red    0     0 
    m    blue    0     0 
          .... 

我目前几乎实现这一目标，但“可选颜色”是给做“笛卡尔积”当我的烦恼：我没有显示空。 ..

这就是我所拥有的。

var boxesInputs = dbContext.BoxesInputs 
.Where(c => c.BoxId == 12) 
.GroupBy(c => new { c.CategoryId, c.ColorId }) 
.Select(g => new 
{ 
    categoryId = g.Key.CategoryId, 
    colorId = g.Key.ColorId, 
    sumOfWeights = g.Sum(r => (decimal?)r.Weight) ?? 0, 
}).ToList(); 

var boxesOutputs = dbContext.BoxesOutputs 
.Where(c => c.BoxId == 12) 
.GroupBy(c => new { c.CategoryId, c.ColorId }) 
.Select(g => new 
{ 
    categoryId = g.Key.CategoryId, 
    colorId = g.Key.ColorId, 
    sumOfWeights = g.Sum(r => (decimal?)r.Weight) ?? 0, 
}).ToList(); 

var categoriesAndColors = dbContext.Categories.AsEnumerable() 
.SelectMany(category => dbContext.Colors.AsEnumerable() 
.Select(color => new 
{ 
    category = new 
    { 
     categoryId = category.CategoryId, 
     name = category.Name, 
    }, 
    color = new 
    { 
     colorId = color.ColorId, 
     name = color.Name, 
    }, 
    inputWeightsSum = boxesInputs.Where(r => r.categoryId == category.CategoryId && r.colorId == color.ColorId).Sum(r => (decimal?) r.sumOfWeights) ?? 0, 
    outputWeightsSum = boxesOutputs.Where(r => r.categoryId == category.CategoryId && r.colorId == color.ColorId).Sum(r => (decimal?)r.sumOfWeights) ?? 0, 
})).ToList(); 

在上面的代码中，前两个查询返回的：

category.name color.name  inputWeightsSum 
------------------------------------------------------- 
    c    null    0 
    c    red    0 
    c    blue    0 
    m    null    0 
    m    red    0 
    m    blue    0 
          .... 

    category.name color.name  outputWeightsSum 
------------------------------------------------------- 
    c    null    0 
    c    red    0 
    c    blue    0 
    m    null    0 
    m    red    0 
    m    blue    0 
          .... 

，第三个加入这两个。我想我需要改进这个连接，因为我失去了空值。

另外，这段代码使用内存中的代码，我希望它是一个单一的sql查询（linq-to-entities而不是linq-to-objects与linq-to-entities混合）。可能吗？因为BoxOutput和BoxInput是两个不同的表格，它们不是直接相连的。不管怎样，最终我最终会得到3个查询？

Answer 1

您从两个表中选择一个相同的匿名类型，将它们合并在一起，然后执行您的组并选择。这样的事情：

dbContext.BoxesInputs 
.Select(g => new TempClass 
{ 
    CategoryId = g.CategoryId, 
    ColorId = g.ColorId, 
    InputWeight = r.Weight, 
    OutputWeight = 0, 
}) 
.Union(dbContext.BoxesOutputs 
    .Select(g => new TempClass 
    { 
     CategoryId = g.CategoryId, 
     ColorId = g.ColorId, 
     InputWeight = 0, 
     OutputWeight = r.Weight 
    }) 
) 
.GroupBy(c => new { c.CategoryId, c.ColorId }) 
.Select(g => new 
{ 
    categoryId = g.Key.CategoryId, 
    colorId = g.Key.ColorId, 
    sumOfInputWeights = g.Sum(r => r.InputWeight), 
    sumOfOutputWeights = g.Sum(r => r.OutputWeight), 
}).ToList(); 

public class TempClass 
{ 
    public int CategoryID { get; set; } 
    public int ColorID { get; set; } 
    public decimal InnerWeight { get; set; } 
    public decimal OuterWeight { get; set; } 
}