我如何判断 StreamReader.Readline() 末尾是否有 environment.newline

Question

我试图逐行读取一个文本文件，并从多行中创建一行，直到读入的行末尾有 \r\n。我的数据如下所示：

BusID|Comment1|Text\r\n
1010|"Cuautla, Inc. d/b/a 3 Margaritas VIII\n
State Lic. #40428210000   City Lic.#4042821P\n
9/26/14      9/14/14 - 9/13/15    5.00\n
9/20/00    9/14/00 - 9/13/01    5.00 New License"\r\n
1020|"7-Eleven Inc., dba 7-Eleven Store #20638\n
State Lic. #24111110126; City Lic. #2411111126P\n
SEND ISSUED LICENSES TO DALLAS, TX\r\n

我希望数据看起来像这样：

BusID|Comment1|Text\r\n
1010|"Cuautla, Inc. d/b/a 3 Margaritas VIII State Lic. #40428210000   City Lic.#4042821P 9/26/14      9/14/14 - 9/13/15    5.00 9/20/00    9/14/00 - 9/13/01    5.00 New License"\r\n
1020|"7-Eleven Inc., dba 7-Eleven Store #20638 State Lic. #24111110126; City Lic. #2411111126P SEND ISSUED LICENSES TO DALLAS, TX\r\n

我的代码是这样的：

FileStream fsFileStream = new FileStream(strInputFileName, FileMode.Open, 
FileAccess.Read, FileShare.ReadWrite);

using (StreamReader srStreamRdr = new StreamReader(fsFileStream))
{
    while ((strDataLine = srStreamRdr.ReadLine()) != null && !blnEndOfFile)
    {
        //code evaluation here
    }

我试过：

if (strDataLine.EndsWith(Environment.NewLine))
{
    blnEndOfLine = true;
}

和

if (strDataLine.Contains(Environment.NewLine))
{
    blnEndOfLine = true;
}

这些在字符串变量的末尾看不到任何东西。有没有办法告诉我真正的行尾，以便我可以将这些行组合成一行？我应该以不同的方式阅读文件吗？

Answer 1

如果您发布的内容与文件中的内容完全一致。意思是 \r\n 确实写好了，你可以使用下面的命令来取消转义：

strDataLine.Replace("\r", "\r").Replace("\n", "\n");

这将确保您现在可以使用 Environment.NewLine 进行比较，如：

if (strDataLine.Replace("\r", "\r").Replace("\n", "\n").EndsWith(Environment.NewLine))
{
    blnEndOfLine = true;
}

Answer 2

您不能使用StringReader 的ReadLine 方法，因为每种换行符。 \r\n 和 \n 都从输入中删除，reader 返回一行，您永远不会知道删除的字符是 \r\n 还是只是 \n

如果文件不是很大，那么您可以尝试将所有内容加载到内存中，然后将自己拆分成单独的行

// Load everything in memory
string fileData = File.ReadAllText(@"D:\temp\myData.txt");

// Split on the \r\n (I don't use Environment.NewLine because it 
// respects the OS conventions and this could be wrong in this context
string[] lines = fileData.Split(new string[] { "\r\n"}, StringSplitOptions.RemoveEmptyEntries);

// Now replace the remaining \n with a space 
lines = lines.Select(x => x.Replace("\n", " ")).ToArray();

foreach(string s in lines)
   Console.WriteLine(s);

编辑
如果你的文件真的很大（比如你说的 3.5GB），那么你无法将所有内容加载到内存中，但你需要分块处理它。幸运的是，StreamReader 提供了一个名为 ReadBlock 的方法，允许我们实现这样的代码

// Where we store the lines loaded from file
List<string> lines = new List<string>();

// Read a block of 10MB
char[] buffer = new char[1024 * 1024 * 10];
bool lastBlock = false;
string leftOver = string.Empty;

// Start the streamreader
using (StreamReader reader = new StreamReader(@"D:\temp\localtext.txt"))
{
    // We exit when the last block is reached
    while (!lastBlock)
    {
        // Read 10MB
        int loaded = reader.ReadBlock(buffer, 0, buffer.Length);

        // Exit if we have no more blocks to read (EOF)
        if(loaded == 0) break;

        // if we get less bytes than the block size then 
        // we are on the last block 
        lastBlock = (loaded != buffer.Length);

        // Create the string from the buffer
        string temp = new string(buffer, 0, loaded);

        // prepare the working string adding the remainder from the 
        // previous loop
        string current = leftOver + temp;

        // Search the last \r\n
        int lastNewLinePos = temp.LastIndexOf("\r\n");

        if (lastNewLinePos > -1)
        {
             // Prepare the working string
             current = leftOver + temp.Substring(0, lastNewLinePos + 2);

             // Save the incomplete parts for the next loop
             leftOver = temp.Substring(lastNewLinePos + 2);
        }
        // Process the lines
        AddLines(current, lines);
    }
}

void AddLines(string current, List<string> lines)
{
    var splitted = current.Split(new string[] { "\r\n" }, StringSplitOptions.RemoveEmptyEntries);
    lines.AddRange(splitted.Select(x => x.Replace("\n", " ")).ToList());
}

此代码假定您的文件始终以 \r\n 结尾，并且您始终在 10MB 的文本块中获得 \r\n。需要对您的实际数据进行更多测试。

Answer 3

您可以通过调用 File.ReadAllText(path) 读取所有文本并按以下方式解析它：

            string input =  File.ReadAllText(your_file_path);
            string output = string.Empty;
            input.Split(new[] { Environment.NewLine } , StringSplitOptions.RemoveEmptyEntries).
                Skip(1).ToList().
                ForEach(x =>
                {
                    output += x.EndsWith("\r\n") ? x + Environment.NewLine 
                                                   : x.Replace("\n"," ");
                });

我如何判断 StreamReader.Readline() 末尾是否有 environment.newline

How can I tell if there is an environment.newline at the end of StreamReader.Readline()

c#

wpf

streamreader

end-of-line