Question

我正在尝试创建一个包装器，用于从单个阵列中选择多个项目。我在下面的代码结尾处得到了结果。不知道我做错了什么。

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

namespace Tester.cs
{
class Program
{
    static void Main(string[] args)
    {
        var customers = new[] 
        {
            new { CustomerID = 1, FirstName = "Orlando", LastName = "Gee",
            CompanyName = "A Bike Store" },
            new { CustomerID = 2, FirstName = "Keith", LastName = "Harris",
            CompanyName = "Bike World" },
            new { CustomerID = 3, FirstName = "Donna", LastName = "Carreras",
            CompanyName = "A Bike Store" },
            new { CustomerID = 4, FirstName = "Janet", LastName = "Gates",
            CompanyName = "Fitness Hotel" },
            new { CustomerID = 5, FirstName = "Lucy", LastName = "Harrington",
            CompanyName = "Grand Industries" },
            new { CustomerID = 6, FirstName = "David", LastName = "Liu",
            CompanyName = "Bike World" },
            new { CustomerID = 7, FirstName = "Donald", LastName = "Blanton",
            CompanyName = "Grand Industries" },
            new { CustomerID = 8, FirstName = "Jackie", LastName = "Blackwell",
            CompanyName = "Fitness Hotel" },
            new { CustomerID = 9, FirstName = "Elsa", LastName = "Leavitt",
            CompanyName = "Grand Industries" },
            new { CustomerID = 10, FirstName = "Eric", LastName = "Lang",
            CompanyName = "Distant Inn" }
                        };

        var addresses = new[] { 
            new { CompanyName = "A Bike Store", City = "New York", Country = "United States"},
            new { CompanyName = "Bike World", City = "Chicago", Country = "United States"},
            new { CompanyName = "Fitness Hotel", City = "Ottawa", Country = "Canada"},
            new { CompanyName = "Grand Industries", City = "London", Country = "United Kingdom"},
            new { CompanyName = "Distant Inn", City = "Tetbury", Country = "United Kingdom"}
        };

        IEnumerable<Names> customerfullName = customers.Select(data => new Names { 
        FirstName = data.FirstName,
        LastName = data.LastName});

        foreach (Names entry in customerfullName)
        {
            Console.WriteLine(entry);
        }  
    }
} 
    class Names
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}

Tester.cs.Names是我在运行程序时重复的内容。

Answer 1

Console.WriteLine使用ToString类的object方法。默认情况下，它显示类的名称。

此方法被派生自object的类重写，以显示他们想要的内容。你没有覆盖它，所以你得到了默认值。

您可以在没有LINQ的情况下重现您的问题，如下所示：

class Names
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

var name = new Names {FirstName = "John", LastName = "Saunders"};
Console.WriteLine(name);  // Will display "Tester.cs.Names"

Answer 2

您的Names类没有覆盖ToString方法，因此它使用object中的默认实现并打印出它的类型名称。您需要覆盖ToString中的Names以打印出基础字符串，或者需要在foreach循环中打印出各个字符串属性。

Answer 3

默认使用ToString，使用：

class Names
{
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public override string ToString()
    {
        return string.Format("{0} {1}", FirstName, LastName);
    }
}

还可以为全名

创建额外的属性

class Names
{
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public string FullName
    {
        get
        {
            return string.Format("{0} {1}", FirstName, LastName);
        }
    }
}

用法：

foreach (Names entry in customerfullName)
{
    Console.WriteLine(entry.FullName);
}

如何显示类的成员

3 个答案: