StreamReader输出

Question

在C#中，为什么这两个代码的输出是不同的？

StreamReader test = new StreamReader(@"C:\a.txt");

while (test.ReadLine() != null)
{
    Console.WriteLine(test.ReadLine());
}

这段代码是：

StreamReader test = new StreamReader(@"C:\a.txt");

string line = "";

while ((line = test.ReadLine()) != null)
{
    Console.WriteLine(line);
} 

Answer 1

每次调用test.ReadLine()都会读取一行新行，因此第一段代码会跳过其中的一半。

Answer 2

在您的第一个示例中，改用以下代码：

while(!test.EndOfStream)
{
   Console.WriteLine(test.ReadLine());
}

Answer 3

由于以下原因，这两个代码的工作方式都是一样的，只是有一点魔力：

test.ReadLine(): ：返回输入流的下一行，如果到达输入流的末尾，则返回null。

      // So,Let's say your a.txt contain the following cases:
       case 1:"Hello World"
       while (test.ReadLine() != null)
        {
            Console.WriteLine("HI" + test.ReadLine());
        }

   // since,we have only one line ,so next line is null and finally it reached the EOD.

    case 2:"Hello World"
   "I am a coder"
       while (test.ReadLine() != null)
        {
            Console.WriteLine("HI" + test.ReadLine());
        }

  // since,we have  two line so ,next line is "I am a coder".
 //It returns:Hi I am a coder.


// And in the below code we are reading and assigning to string variable

        StreamReader test1 = new StreamReader(@"D:\a.txt");

        string line = "";

        while ((line = test1.ReadLine()) != null)
        {
            Console.WriteLine(line);
        }