（应该很简单）LINQ问题 [英] (Should be really simple) LINQ question

问题描述

根据我的书，我以为我理解LINQ。我没有。



我想做的就是加一些数字。我的代码如下。不编译的位是显而易见的。

我的问题是我做错了什么？我想做的就是将数字加1 + 2 + 5 - 1000 + 100 = -892，但我甚至不能这样做。



请有人帮帮我。



谢谢

Hi, I thought I understood LINQ according to my book. I don't.

All I want to do is sum some numbers. My code is below. The bit that doesn't compile is obvious.
My question is what am I doing wrong? All I want to do is sum the numbers 1 + 2 + 5 - 1000 + 100 = -892 but I can't even do that.

Please please can someone help me out here.

Thank you

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

namespace ConsoleApplication7
{
    class C3
    {
        public C3(int foo) { Foo = foo; }
        public int Foo { get; set; }
    }

    class C2
    {
        public C2(List<C3> bar) { Bar = bar; }
        public List<C3> Bar { get; set; }
    }

    class C1
    {
        public C1(List<C2> baz) { Baz = baz; }
        public List<C2> Baz { get; set; }
    }


    class Program
    {
        public void Run()
        {
            C2 c2_1 = new C2(new List<C3> {new C3(1), new C3(2), new C3(5)});
            C2 c2_2 = new C2(new List<C3> { new C3(-1000), new C3(100) });

            C1 c1 = new C1(new List<C2>() { c2_1, c2_2 });

            //Answer = -892, but I can't even get the syntax right for it to compile
            var resultSum = c1.Baz.Select(x => x.Bar).Sum(y => y.Foo);

        }
        static void Main(String[] args)
        {
            new Program().Run();
        }
    }
}

推荐答案

我认为Baz.Select返回列表列表， NL。 Bar的列表（这是一个列表）ants lsit没有属性Foo

你试过SelectMany吗？

I think Baz.Select returns a list of lists, nl. a list of Bar (which is a list) ant the lsit does not have property Foo
Have you tried SelectMany ?

嗨Serge，是的我也试过SelectMany ，代码如下：

Hi Serge, yes I tried SelectMany too, code below:

var resultSum = c1.Baz.Select(x => x.Bar).SelectMany(y => y.Foo).Sum(z => z);

我无法得到这个虽然我认为语法是正确的，但它显然不是。

I cant get this to compile either so although I think the syntax is correct, it clearly is not.

你可以这样做：

you can do it like that:

var resultSum = c1.Baz.SelectMany(x => // selecting all Bars as one IEnumerable
    x.Bar).Sum(x => // summing all Foos.
        x.Foo);

ps：请发表评论作为评论，不是解决方案。

ps: please send your comment as comment, not a solution.

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