Question

我试图通过在WinForm应用程序中使用以下代码将数据保存到ArrayList（）。问题是当我这样做时，bookList.txtBookList.Text中的输出是Lab_8.Book，我无法弄清楚原因。希望有一些提示。

BookEntry.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace Lab_8
{
    public partial class BookEntry : Form
    {
        private ArrayList books = new ArrayList();
        private BookList bookList = new BookList();

        public BookEntry()
        {
            InitializeComponent();
        }

        private void btnEnter_Click(object sender, EventArgs e)
        {
            books.Add(new Book(txtTitle.Text, txtFirstName.Text, 
                txtLastName.Text, txtPublisher.Text, 
                float.Parse(txtPrice.Text)));
        }

        private void btnShowBooks_Click(object sender, EventArgs e)
        {
            foreach (object list in books)
            {
                bookList.txtBookList.Text += list.ToString() + "\n";
            }

            bookList.ShowDialog();
        }
    }
}

Book.cs

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

namespace Lab_8
{
    class Book : Publication
    {
        private string authorFirstName, authorLastName;

        public Book()
        { }

        public Book(string title, string firstName, string lastName, string publisherName, float price)
        : base(title, publisherName, price)
        {
            this.authorFirstName = firstName;
            this.authorLastName = lastName;
        } 

        public string getAuthorName()
        {
            return authorFirstName + " " + authorLastName;
        }

        public string AuthorFirstName
        {
            get
            {
                return authorFirstName;
            }
            set
            {
                authorFirstName = value;
            }
        }
        public string AuthorLastName
        {
            get
            {
                return authorLastName;
            }
            set
            {
                authorLastName = value;
            }
        }
    }
}

的问候。 HelpNeeder

Answer 1

这里的问题是Book没有覆盖ToString，这意味着这个循环：

foreach (object list in books)
{
  bookList.txtBookList.Text += list.ToString() + "\n";
}

只打印出类的名称（带命名空间）或Lab_8.Book。

要解决此问题，您可以Book中的override ToString()：

class Book : Publication
{
   // .. Your code...

   public override string ToString()
   {
       return this.Title + " by " + this.AuthorFirstName + " " + this.AuthorLastName;
   }

话虽如此，我强烈建议您将ArrayList转换为使用List<Book>。这将允许您直接将书籍称为书籍，即：

foreach (Book book in books)
{
  bookList.txtBookList.Text += book.AuthorFirstName + Environment.NewLine;
}

唯一需要改变的是：

private ArrayList books = new ArrayList();

要：

private List<Book> books = new List<Book>();

然后还要更改上面的列表......

Answer 2

您应该将ArrayList转换为List。

然后，您将拥有一个强类型List Book以及IEnumerable界面的所有好处。这将使您的代码更容易阅读。

因为你有

foreach (object book in books)

这将采用ToString()的默认实施，因为book为System.Object。调用System.Object.ToString()将返回该类的名称。在这种情况下，Lab_8.Book。

使用非默认构造函数向ArrayList（）添加条目

2 个答案: