[英]Iterate through list of items to their parent and parent to parent level
我有一个要求遍历具有 n 级层次结构的项目列表,并且我想获取所选项目 ID 的自下而上元素。
例如,下面是原始数据
ID ParentID ItemName Category
1 -1 Chai Breweries
4 -1 Mouse-pad Electronic
3 1 GST Taxes
2 1 Spices
5 4 Mobile
6 3 My Tax
我想在 C# 中编程以进行迭代并显示例如,如果我为方法 6 传递 ID 参数,那么它应该打印 output 如下
ParentID=3, Name=My Tax, Category=Taxes
如果我将 ID 参数作为 2 传递,那么 output 应该是相似的
ParentID=1, Name=Spices, Category=Breweries
请帮助我实现此功能可能是使用通用集合或任何算法都会有帮助
我尝试过使用 List 并加上 LINQ 的 select 很多,但是使用此选项,我只能获取当前项目,但如果当前项目没有与之关联的类别,则不能获取父类别值。 还尝试添加递归方法,但不确定如何构建结束 output,使用递归我们应该只获取当前项目。
好的,根据以下评论,我使用了递归 function 如下
class Program
{
static void Main(string[] args)
{
int categoryId = 202;
var products = GetProducts();
var product = products.FirstOrDefault(p => p.ID == categoryId);
var output = GetProductRecursively(products, categoryId, string.Empty);
Console.WriteLine(output);
Console.Read();
}
public static string GetProductRecursively(List<Product> products, int parentId, string output)
{
var product = products.FirstOrDefault(p => p.ParentID == parentId);
StringBuilder stringBuilder = new StringBuilder();
if (string.IsNullOrEmpty(product.Category))
{
if (string.IsNullOrEmpty(output))
{
stringBuilder.Append($"ParentCategoryID={ product.ParentID}, Name={ product.ItemName}, Keywords=");
GetProductRecursively(products, product.ParentID, stringBuilder.ToString());
}
else
GetProductRecursively(products, product.ParentID, output);
}
else
stringBuilder.Append($"{output}{product.Category}");
return stringBuilder.ToString();
}
public static List<Product> GetProducts()
{
var products = new List<Product>();
products.Add(new Product { ID = 1, ParentID = -1, ItemName = "Chai", Category = "Breweries" });
products.Add(new Product { ID = 4, ParentID = -1, ItemName = "Mouse-pad", Category= "Electronic" });
products.Add(new Product { ID = 3, ParentID = 1, ItemName = "GST", Category= "Taxes" });
products.Add(new Product { ID = 2, ParentID = 1, ItemName = "Spices" });
products.Add(new Product { ID = 5, ParentID = 4, ItemName = "Mobile" });
products.Add(new Product { ID = 6, ParentID = 3, ItemName = "My Tax" });
return products;
}
}
public class Product
{
public int ID { get; set; }
public int ParentID { get; set; }
public string ItemName { get; set; }
public string Category { get; set; }
}
但是,在一次迭代中,它返回父 ID 的类别,但由于它处于递归状态,因此它继续完成早期迭代的工作,因此此时类别始终返回“”(empty.string)
非递归解决方案可能如下所示:
var productId = 6;
var products = GetProducts();
var productDict = products // create dictionary to search for products by id
.GroupBy(p => p.ID)
.ToDictionary(p => p.Key, g => g.First());
var product = productDict[productId];
// create loop state variables
string category = null;
var currProduct = product;
// cycle while category not found
while (category == null)
{
// or there is no parent product
if (!productDict.ContainsKey(currProduct.ParentID))
{
break;
}
currProduct = productDict[currProduct.ParentID];
category = currProduct.Category;
}
Console.WriteLine($"{category}-{product.ItemName}");
没有任何代码,我只能为您的问题提供“默认”答案。
要解决您的问题,您必须在类中实现 function 以获取实例的父级。
要获得绝对父级(对象本身没有父级),您必须实现一个 function,只要它有父级,它就会调用自己。
好的,终于让它以正确的逻辑工作,工作代码如下
class Program
{
static void Main(string[] args)
{
int productId = 6;
var products = GetProducts();
var product = products.FirstOrDefault(p => p.ID == productId);
var output = GetProductRecursively(products, productId, string.Empty);
Console.WriteLine(output);
Console.Read();
}
public static string GetProductRecursively(List<Product> products, int Id, string output)
{
var product = products.FirstOrDefault(p => p.ID == Id);
StringBuilder stringBuilder = new StringBuilder();
if (string.IsNullOrEmpty(output))
output = stringBuilder.Append($"ParentCategoryID={ product.ParentID}, Name={ product.ItemName}, Keywords=").ToString();
if (string.IsNullOrEmpty(product.Category))
{
return GetProductRecursively(products, product.ParentID, output);
}
else
output += $"{product.Category}";
return output;
}
public static List<Product> GetProducts()
{
var products = new List<Product>();
products.Add(new Product { ID = 1, ParentID = -1, ItemName = "Chai", Category = "Breweries" });
products.Add(new Product { ID = 4, ParentID = -1, ItemName = "Mouse-pad", Category = "Electronic" });
products.Add(new Product { ID = 3, ParentID = 1, ItemName = "GST", Category = "Taxes" });
products.Add(new Product { ID = 2, ParentID = 1, ItemName = "Spices" });
products.Add(new Product { ID = 5, ParentID = 4, ItemName = "Mobile" });
products.Add(new Product { ID = 6, ParentID = 3, ItemName = "My Tax" });
return products;
}
}
public class Product
{
public int ID { get; set; }
public int ParentID { get; set; }
public string ItemName { get; set; }
public string Category { get; set; }
}
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