英文:
Linq group query
问题
你想要使用C#的LINQ查询来实现这个转换。以下是一个可能的解决方案：
using System;
using System.Collections.Generic;
using System.Linq;
public class Product
{
public int ProductId { get; set; }
public string CategoryName { get; set; }
public string CategoryValue { get; set; }
}
public class ProductwithCategory
{
public int ProductId { get; set; }
public Dictionary<string, string> allCategoriesWithvalue { get; set; } = new Dictionary<string, string>();
}
public class Program
{
public static void Main()
{
List<Product> products = new List<Product>
{
new Product { ProductId = 1, CategoryName = "A", CategoryValue = "AV" },
new Product { ProductId = 1, CategoryName = "B", CategoryValue = "BV" },
new Product { ProductId = 1, CategoryName = "C", CategoryValue = "CV" },
new Product { ProductId = 2, CategoryName = "B", CategoryValue = "BV" },
new Product { ProductId = 3, CategoryName = "C", CategoryValue = "CV" }
};
var transformedData = products
.GroupBy(p => p.ProductId)
.Select(g => new ProductwithCategory
{
ProductId = g.Key,
allCategoriesWithvalue = g.ToDictionary(p => p.CategoryName, p => p.CategoryValue)
})
.ToList();
foreach (var item in transformedData)
{
Console.WriteLine($"ProductId: {item.ProductId}");
foreach (var category in item.allCategoriesWithvalue)
{
Console.WriteLine($"{category.Key}: {category.Value}");
}
Console.WriteLine();
}
}
}
这段代码首先创建了一个Product类和一个ProductwithCategory类，分别表示原始数据和转换后的数据。然后，使用LINQ查询对原始数据进行分组和转换，生成转换后的数据。最后，通过循环遍历转换后的数据并打印结果。
请注意，这只是一种可能的实现方式，你可以根据自己的需求进行调整和优化。
英文:
I have this model data
public class Product
{
public int ProductId { get; set; }
public string CategoryName { get; set; }
public string CategoryValue { get; set; }
}
Data
[
{
"productId": 1,
"categoryName": "A",
"categoryValue": "AV"
},
{
"productId": 1,
"categoryName": "B",
"categoryValue": "BV"
},
{
"productId": 1,
"categoryName": "C",
"categoryValue": "CV"
},
{
"productId": 2,
"categoryName": "B",
"categoryValue": "BV"
},
{
"productId": 3,
"categoryName": "C",
"categoryValue": "CV"
}
]
I want to transform into that model through linq
public class ProductwithCategory
{
public int ProductId { get; set; }
public Dictionary<string, string> allCategoriesWithvalue { get; set; } = new Dictionary<string, string>();
}
Transformed data (finial result)
[
{
"productId": 1,
"allCategoriesWithvalue": {
"A": "AV",
"B": "BV",
"C": "CV"
}
},
{
"productId": 2,
"allCategoriesWithvalue": {
"A": "",
"B": "BV",
"C": ""
}
},
{
"productId": 3,
"allCategoriesWithvalue": {
"A": "",
"B": "",
"C": "CV"
}
}
]
I want to c# linq query for that
答案1
得分: 1
要在类别缺失时获得空值，可以使用左连接（left join）与类别的唯一集合进行连接。
var l = new List<Product>()
{
new Product() { ProductId = 1, CategoryName = "A", CategoryValue = "AV" },
new Product() { ProductId = 1, CategoryName = "B", CategoryValue = "BV" },
new Product() { ProductId = 1, CategoryName = "C", CategoryValue = "CV" },
new Product() { ProductId = 2, CategoryName = "B", CategoryValue = "BV" },
new Product() { ProductId = 3, CategoryName = "C", CategoryValue = "CV" },
};
var categories = l.Select(x => x.CategoryName).Distinct().ToList();
var r = l
.GroupBy(x => x.ProductId)
.Select(x => new ProductwithCategory()
{
ProductId = x.Key,
allCategoriesWithvalue = (from c in categories
join p in x on c equals p.CategoryName into ps
from p in ps.DefaultIfEmpty()
select new { c, p?.CategoryValue }).ToDictionary(x => x.c, x => x.CategoryValue ?? "")
});
请注意，这是一段C#代码，用于在给定的产品列表中，根据产品ID对产品进行分组，并将每个产品的类别和对应的值存储在字典中。如果某个类别在产品列表中不存在，则对应的值将为空字符串。
英文:
To get an empty value when the category is missing you left join with a distinct collection of the categories.
var l = new List<Product>()
{
new Product() { ProductId = 1, CategoryName = "A", CategoryValue = "AV" },
new Product() { ProductId = 1, CategoryName = "B", CategoryValue = "BV" },
new Product() { ProductId = 1, CategoryName = "C", CategoryValue = "CV" },
new Product() { ProductId = 2, CategoryName = "B", CategoryValue = "BV" },
new Product() { ProductId = 3, CategoryName = "C", CategoryValue = "CV" },
};
var categories = l.Select(x => x.CategoryName).Distinct().ToList();
var r = l
.GroupBy(x => x.ProductId)
.Select(x => new ProductwithCategory()
{
ProductId = x.Key,
allCategoriesWithvalue = (from c in categories
join p in x on c equals p.CategoryName into ps
from p in ps.DefaultIfEmpty()
select new { c, p?.CategoryValue }).ToDictionary(x => x.c, x => x.CategoryValue ?? "")
});
答案2
得分: 0
你必须首先按ProductId进行分组，并将productId作为键。然后在名为allCategoriesWithvalue的字典中选择CategoryName和CategoryValue。
products.GroupBy(p => p.ProductId)
.Select(group => new ProductwithCategory
{
ProductId = group.Key,
allCategoriesWithvalue = group.ToDictionary(p => p.CategoryName, p => p.CategoryValue)
}).ToList();
英文:
You must group by ProductId first and consider productId as key. Then select CategoryName and CategoryValue in a dictionary called allCategoriesWithvalue.
products.GroupBy(p => p.ProductId)
.Select(group => new ProductwithCategory
{
ProductId = group.Key,
allCategoriesWithvalue = group.ToDictionary(p => p.CategoryName, p => p.CategoryValue)
}).ToList();
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