Question

我需要从文本文件中读取，然后将每行放入列表中，然后从该列表中读取。但我得到一个NullReferenceException“对象引用未设置为对象的实例。”在7个线下的同时例外。我已经尝试了我能想到的一切。提前谢谢。

                StreamReader sre = new StreamReader(FILE_PATH);
                Books books = new Books();
                string line;
                while ((line = sre.ReadToEnd()) != null)
                {
                 //NullReferenceException is Right here
                 //I defined myLibraryBooks outside of this code; But it is in the same scope
                    myLibraryBooks.Add(new Books() { Author = books.Author.ToUpper(), Title = line.ToUpper(), ISBN = line, Publish_Date = line });
                }
                Console.Write("Enter Author's Name:");
                string input_to_find = Console.ReadLine();
                var author = from Authors in myLibraryBooks
                             where Authors.Author == input_to_find
                             select Authors;

                foreach (var book in author)
                {
                    Console.WriteLine(String.Format("      Author            Title            ISBN            Publish Date"));
                    Console.WriteLine(String.Format("       {0}          {1}              {2}                {3}", books.Author, books.Title, books.ISBN, books.Publish_Date));
                }
                sre.Dispose();

Answer 1

你声明books，但它看起来并没有被设置为任何东西（除非你在构造函数中做了一些奇怪的事情）。基于此，我想说以下行可能会导致此异常：

      *Guessing Author is null...
books.Author.ToUpper()

利用.NET的调试工具，逐行逐步查看代码，了解问题所在。

如何从文本文件读取到列表并从该列表中读取C＃

1 个答案: