C# Linq 在对象列表中查找对象列表中的值

Question

I created a simple setup to try to write the appropriate Linq statement in C#.

I'm trying to return a BOOLEAN that checks the following

1. Example 1: Where Product title = 'ERDSIC' and Property title = 'size' and val = 1001 (should return TRUE)
2. Example 2: Where Product title = 'ERDCON' and Property title = 'size' and val = 1001 (should return FALSE)

I attempted my own Linq statement which is producing a boolean inside an object, but I can't get it to return an actual boolean.

How can I write a Linq statement that will fit the following criteria for Example 1 and Example 2?

var result = listProducts
               .Where(a => a.title == "ERDSIC").Select(
                  a => a.listProperties.Where(b => b.title == "size").Select(
                      c => c.listValues.Where(d => d.val == 1001).Any()
                  )
               );

    Console.WriteLine(result.ToString()); 
    //returns:  System.Linq.Enumerable+WhereSelectListIterator`2[Program+Product,System.Collections.Generic.IEnumerable`1[System.Boolean]]

TEST PROGRAM:

using System.Collections.Generic;
using System;
using System.Linq;

public class Program
{
  public class Value {
    public int id {get;set;}
    public int val {get;set;}
  }

  public class Property {
    public int id {get;set;}    
    public string title {get;set;}
    public List<Value> listValues {get;set;}
  }


  public class Product {
    public int id {get;set;}
    public string title {get;set;}
    public List<Property> listProperties {get;set;}
  }

  public static void Main()
  {
    List<Product> listProducts = new List<Product> 
    {
        new Product { 
            id = 1, 
            title = "ERDCON",
            listProperties = new List<Property> {
                new Property {
                    id = 1, 
                    title = "voltage",
                    listValues = new List<Value> {
                        new Value {id = 1, val = 7},
                        new Value {id = 2, val = 12},
                        new Value {id = 3, val = 21}
                    }
                },
                new Property {
                    id = 2, 
                    title = "size",
                    listValues = new List<Value> {
                        new Value {id = 4, val = 101},
                        new Value {id = 5, val = 102},
                        new Value {id = 6, val = 103},
                        new Value {id = 7, val = 104}
                    }
                }
            }
        },

        new Product { 
            id = 14, 
            title = "ERDSIC",
            listProperties = new List<Property> {
                new Property {
                    id = 31, 
                    title = "direction",
                    listValues = new List<Value> {
                        new Value {id = 18, val = 0},
                        new Value {id = 21, val = 1}
                    }
                },
                new Property {
                    id = 1, 
                    title = "size",
                    listValues = new List<Value> {
                        new Value {id = 68, val = 1001},
                        new Value {id = 71, val = 1004}
                    }
                }
            }
        }       
    };


    //Example 1: Check if List<Product> contains "Product Title='ERDSIC', "Property title='size', and "val = 1001"
    //result should return TRUE



    //Example 2: Check if List<Product> contains "Product Title='ERDCON', "Property title='size', and "val = 1001"
    //result should return FALSE







  }
}

Answer 1

You should replace the Where method with Any mostly, because Where returns filtered sequence, when Any determines whether any element of a sequence satisfies a condition

var result = listProducts.Any(product =>
    product.title == "ERDSIC" && product.listProperties.Any(property =>
        property.title == "size" && property.listValues.Any(v => v.val == 1001)));

However, it's better to wrap this code into method, like extension one, and call with different arguments

public static class Ext
{
    public static bool HasTitleAndSize(this IEnumerable<Product> products, string title, int size)
    {
        return products.Any(product =>
            product.title == title && product.listProperties.Any(property =>
                property.title == "size" && property.listValues.Any(v => v.val == size)));
    }
}

And call in the following way

var result = listProducts.HasTitleAndSize("ERDSIC", 1001); //returns true
result = listProducts.HasTitleAndSize("ERDCON", 1001); //returns false

Answer 2

Trying to mimic your style, first query may look like:

var result = listProducts
    .Where(a => a.title == "ERDSIC")
    .SelectMany(a => a.listProperties)
    .Where(b => b.title == "size")
    .SelectMany(c => c.listValues)
    .Where(d => d.val == 1001)
    .Any();