LINQ的 - 通過性能兒童相交2所列出對象

Question

我試圖合併兩個列表。我經常這樣做成功的時候我已經合併類似ProductsList1.Product.Id與ProductList2.Product.Id，但是在這種情況下，它更像是ProductsList.Product.Id與ProductCategoriesList.ProductCategory.ProductId。第三級屬性是什麼讓我！

// LIST OF PRODUCTS IN RESULT SETS 
    List<Product> products = new List<Product>(); 
    products.Add(new Product() { Id = 1 }); 
    products.Add(new Product() { Id = 2 }); 

    // LIST OF ALL PRODUCTS AND THEIR CATEGORY TAXONOMIES 
    List<ProductCategory> allProductCategories = new List<ProductCategory>(); 
    allProductCategories.Add(new ProductCategory() { ProductId = 1, CategoryUid = 101, ParentCategoryUid = 30 }); 
    allProductCategories.Add(new ProductCategory() { ProductId = 1, CategoryUid = 30, ParentCategoryUid = 2 }); 
    allProductCategories.Add(new ProductCategory() { ProductId = 1, CategoryUid = 2, ParentCategoryUid = 1 }); 
    allProductCategories.Add(new ProductCategory() { ProductId = 3, CategoryUid = 101, ParentCategoryUid = 43 }); 
    allProductCategories.Add(new ProductCategory() { ProductId = 3, CategoryUid = 43, ParentCategoryUid = 8 }); 
    allProductCategories.Add(new ProductCategory() { ProductId = 3, CategoryUid = 8, ParentCategoryUid = 1 }); 

    // NEED TO MERGE THE 2ND LIST INTO THE 1ST BY PRODUCTID VIA SQL EQUIV INNER JOIN 
    // END RESULT SHOULD BE products list has 2 objects. one object has 1 list product category with 3 child objects 
    // THIS IS THE CLOSEST I GOT 
    products.Select(x => x.Id).Intersect(allProductCategories.Select(a => a.ProductId).ToList()); 
} 

public class Product 
{ 
    private int _id; 
    private List<ProductCategory> _productCategories; 

    public int Id 
    { 
     get { return _id; } 
     set { _id = value; } 
    } 

    public List<ProductCategory> ProductCategories 
    { 
     get { return _productCategories; } 
     set { _productCategories = value; } 
    } 
} 

public class ProductCategory 
{ 
    private int _productId; 
    private int _categoryUid; 
    private int _parentCategoryUid; 

    public int ProductId 
    { 
     get { return _productId; } 
     set { _productId = value; } 
    } 

    public int CategoryUid 
    { 
     get { return _categoryUid; } 
     set { _categoryUid = value; } 
    } 

    public int ParentCategoryUid 
    { 
     get { return _parentCategoryUid; } 
     set { _parentCategoryUid = value; } 
    } 
} 

Answer 1

// LIST OF PRODUCTS IN RESULT SETS 
List<Product> products = new List<Product> { 
    new Product() {Id = 1, ProductCategories = new List<ProductCategory>()}, 
    new Product() {Id = 2, ProductCategories = new List<ProductCategory>()} 
}; 

// LIST OF ALL PRODUCTS AND THEIR CATEGORY TAXONOMIES 
List<ProductCategory> allProductCategories = new List<ProductCategory> 
{ 
    new ProductCategory() {ProductId = 1, CategoryUid = 101, ParentCategoryUid = 30}, 
    new ProductCategory() {ProductId = 1, CategoryUid = 30, ParentCategoryUid = 2}, 
    new ProductCategory() {ProductId = 1, CategoryUid = 2, ParentCategoryUid = 1}, 
    new ProductCategory() {ProductId = 3, CategoryUid = 101, ParentCategoryUid = 43}, 
    new ProductCategory() {ProductId = 3, CategoryUid = 43, ParentCategoryUid = 8}, 
    new ProductCategory() {ProductId = 3, CategoryUid = 8, ParentCategoryUid = 1} 
}; 

// General logic going on here: 
// Add all ProductCategory where the ProductID is equal 
// to the Prdoduct.ID to the current Product.ProductCategories 
products.ForEach(pr=> 
    allProductCategories.Where(pC=> 
     pC.ProductId.Equals(pr.Id)).ToList().ForEach(pC=> 
      pr.ProductCategories.Add(pC))); 

// products.ToList().ForEach(x=>Console.WriteLine(x.ProductCategories.Count)); 

---

輸出：

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我不知道使用交叉方法是否有更簡單的方法，但是這個方法確實有效！

根據documentation（使用Enumerable.Intersect），您需要使用多種類型實現自定義IEqualityComparer。因此，目前不可能做這樣的事情，或者簡單地採用比我當前的解決方案更多的代碼行。

如果你想知道更多關於Enumerable.Intersect，我建議訪問dotnetperls.com！

Answer 2

下面的查詢將做的工作：

var result = products.Join(allProductCategories, p => p.Id, 
           pc => pc.ProductId, (p, pc) => new { p, pc}) 
          .GroupBy(x => x.p.Id) 
          .Select(x => new Product{ Id = x.Key, ProductCategories = x.Select(y => y.pc).ToList()}); 

要求：

• 從兩個不同的名單，其中有共同的標識獲取數據，並創建一個合併版本，其中包含父代Product的Id以及所有匹配的行ProductCategory

說明：

• 內加入的ID兩個列表
• GROUPBY ProductId來彙總ProductCategory數據
• 在單獨收集，其中ID是關鍵，數據選擇它們是所有集合彙總/分組結果

您可以使用Linqpad和result.Dump()運行它，將提供最終結果的清晰視圖t