c# – 玩匿名类型 - 编程之家

从Jon Skeet的精彩书C#深度,第一版：

class Film
{
    public string Name { get; set; }
    public int Year { get; set; }

    public override string ToString()
    {
        return string.Format("Name={0},Year={1}",Name,Year);
    }
}

var films = new List<Film>
{
    new Film {Name="Jaws",Year=1975},new Film {Name="Singing in the Rain",Year=1952},new Film {Name="Some Like It Hot",Year=1959},new Film {Name="The Wizard of Oz",Year=1939},new Film {Name="It's a Wonderful Life",Year=1946},new Film {Name="American Beauty",Year=1999},new Film {Name="High Fidelity",Year=2000},new Film {Name="The Usual SUSPECTs",Year=1995}
};

Action<Film> print = film => { Console.WriteLine(film); };
films.ForEach(print);
films.FindAll(film => film.Year < 1960)
.ForEach(print);
films.sort((f1,f2) => f1.Name.Compareto(f2.Name));
films.ForEach(print);

一段落在上面列出的代码段之后.

The first half of listing 9.4 involves just setting up the data. I would have used an anonymous type,but it’s relatively tricky to create a generic list from a collection of anonymous type instances. (You can do it by creating a generic method that takes an array
and converts it to a list of the same type,then pass an implicitly typed array into that
method. An extension method in .NET 3.5 called ToList provides this functionality
too,but that would be cheating as we haven’t looked at extension methods yet!)

而上面提供的代码片段,是该段所指的书的9.4.

我的问题：
我正在尝试用上面段落中描述的技术(看斜体文字),但我不明白他的意思.

我试过这样的东西,但这不是他的意思,我想,因为它不工作(我没想到)

using System;
using System.Collections.Generic;

namespace ScratchPad
{

class Film
{
    public string Name { get; set; }
    public int Year { get; set; }

    public override string ToString()
    {
        return string.Format("Name = {0}\tYear = {1}",Year);
    }
}

class Program
{
    static void Main(string[] args)
    {
        ToList<Film>( new[]
        {
            new { Name = "north By northwest",Year = 1959 },new { Name = "The Green Mile",Year = 1999},new { Name = "The Pursuit of Happyness",Year = 2006}
        }).ForEach( f => {Console.WriteLine(f);} );

        Console.ReadKey();
    }

    static List<T> ToList<T>(
        System.Collections.IEnumerable list)
    {
        var newList = new List<T>();

        foreach (var thing in list)
            if (thing is T)
                newList.Add((T)thing);

        return newList;

    }
}

}

注意：我知道IEnumerable.ToList()扩展方法,并且已经使用了很多次.我只想手工尝试该段落中概述的技术.

此外,我对匿名类型在Linq之外使用的场景感兴趣,作为句法方便,下面给出了一种这样的场景.我可以随时在C#4中使用动态,并接受一个匿名类型作为参数,并与它一起工作,了解我的期望.我希望我可以用C#3做到这一点.如下所示：

using System;
using Microsoft.CSharp.RuntimeBinder;

namespace PlayWithAnonType
{
    class Program
    {
        static void Main(string[] args)
        {
            PrintThingy(new { Name = "The Secret",Genre = "Documentary",Year = 2006 });
            Console.ReadKey();
        }

    static void PrintWhatever(dynamic whatever)
    {
        // the anonymous type's ToString() will print
        Console.WriteLine(whatever);
    }

    static void PrintThingy(dynamic thingy)
    {
        try
        {
            // I kNow what the thingy is
            Console.WriteLine("Name = {0}\tGenre = {1}\tYear = {2}",thingy.Name,thingy.Genre,thingy.Year);
        }
        catch(RuntimeBinderException ex)
        {
#pragma warning disable 0168
            Console.WriteLine("By thingy,I really meant film. 
Sorry,I should've clarified.");
#pragma warning restore 0168
        }
    }
}

}

编辑
他们应该有一个名为jon-skeet的标签.

解决方法

要做到这一点：

public void Main (string[] args)
{
    var films = ToList(new [] {
        new {Name = "Jaws",Year = 1975},new {Name = "Singing in the Rain",Year = 1952},new {Name = "Some Like It Hot",Year = 1959},new {Name = "The Wizard of Oz",Year = 1939},new {Name = "It's a Wonderful Life",Year = 1946},new {Name = "American Beauty",new {Name = "High Fidelity",Year = 2000},new {Name = "The Usual SUSPECTs",Year = 1995}
    }
    );


    films.ForEach(f => Console.Write(f.Name + " - " + f.Year));

}

public List<T> ToList<T> (IEnumerable<T> list)
{
    return new List<T>(list);
}

正如其他人所说,我不知道这是多么有用.你会得到智能感知和所有这些,当你写,所以可能有一些打字节省,至少？

原文地址：https://www.jb51.cc/csharp/95679.html

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c# – 玩匿名类型

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