Linq查詢，通過與不直接連接

Question

在EF模型使用這些類兩個表涉及做組：

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 
} 

......我該怎麼辦LINQ查詢，對於一個特定的盒（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 
          .... 

我目前幾乎實現這一目標，但「可選顏色」是給做「笛卡爾積」當我的煩惱：我沒有顯示空。 ..

這就是我所擁有的。

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(); 

在上面的代碼中，前兩個查詢返回的：

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 
          .... 

，第三個加入這兩個。我想我需要改進這個連接，因爲我失去了空值。

另外，這段代碼使用內存中的代碼，我希望它是一個單一的sql查詢（linq-to-entities而不是linq-to-objects與linq-to-entities混合）。可能嗎？因爲BoxOutput和BoxInput是兩個不同的表格，它們不是直接相連的。不管怎樣，最終我最終會得到3個查詢？

Answer 1

您從兩個表中選擇一個相同的匿名類型，將它們合併在一起，然後執行您的組並選擇。這樣的事情：

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; } 
}