C# Streamreader - 仅在 {CR}{LF} 处中断

Question

在执行复杂的 SSIS 插入包之前，我正在尝试计算文本文件中的行数（以与控制文件进行比较）。

目前我使用的是 StreamReader，它用嵌入新行的 {LF} 换行，而 SSIS 使用的是 {CR}{LF}（正确），因此计数没有统计。

有谁知道执行此操作的替代方法，我可以仅根据 {CR}{LF} 换行符计算文件中的行数？

提前致谢

Answer 1

{CR}{LF} 是所需的。不能真的说哪个是正确的。

因为 ReadLine 去掉了你不知道的行尾

使用 StreamReader.Read Method () 并查找 13，然后查找 10
它 return 整数

Answer 2

这是一种非常懒惰的方法...这会将整个文件读入内存。

var cnt = File.ReadAllText("yourfile.txt")
              .Split(new[] { "\r\n" }, StringSplitOptions.None)
              .Length;

Answer 3

遍历文件并计算 CRLF 的数量。

非常简单的实现：

public int CountLines(Stream stream, Encoding encoding)
{
    int cur, prev = -1, lines = 0;
    using (var sr = new StreamReader(stream, encoding, false, 4096, true))
    {
        while ((cur = sr.Read()) != -1)
        {
            if (prev == '\r' && cur == '\n')
                lines++;

            prev = cur;
        }
    }

    //Empty stream will result in 0 lines, any content would result in at least one line
    if (prev != -1)
        lines++;

    return lines;
}

用法示例：

using(var s = File.OpenRead(@"<your_file_path>"))
    Console.WriteLine("Found {0} lines", CountLines(s, Encoding.Default));

实际上是在字符串任务中查找子字符串。可以使用更通用的算法。

Answer 4

这是一个扩展方法，它只读取带有行分隔符 {Cr}{Lf} 的行，而不是 {LF}。你可以算一下。

var count=  new StreamReader(@"D:\Test.txt").ReadLinesCrLf().Count()

但也可以用它来读取文件，有时有用，因为正常的 StreamReader.ReadLine 在 {Cr}{Lf} 和 {LF} 上都会中断。可用于任何 TextReader 和工作流（文件大小不是问题）。

    public static IEnumerable<string> ReadLinesCrLf(this TextReader reader, int bufferSize = 4096)
    {
        StringBuilder lineBuffer = null;

        //read buffer            
        char[] buffer = new char[bufferSize];
        int charsRead;

        var previousIsLf = false;

        while ((charsRead = reader.Read(buffer, 0, bufferSize)) != 0)
        {
            int bufferIndex = 0;
            int writeIdx = 0;
            do
            {
                var currentChar = buffer[bufferIndex];
                switch (currentChar)
                {
                    case '\n':
                        if (previousIsLf)
                        {
                            if (lineBuffer == null)
                            {
                                //return from current buffer writeIdx could be higher than 0 when multiple rows are in the buffer                                            
                                yield return new string(buffer, writeIdx, bufferIndex - writeIdx - 1);
                                //shift write index to next character that will be read
                                writeIdx = bufferIndex + 1;
                            }
                            else
                            {
                                Debug.Assert(writeIdx == 0, $"Write index should be 0, when linebuffer != null");
                                lineBuffer.Append(buffer, writeIdx, bufferIndex - writeIdx);
                                Debug.Assert(lineBuffer.ToString().Last() == '\r',$"Last character in linebuffer should be a carriage return now");
                                lineBuffer.Length--;
                                //shift write index to next character that will be read
                                writeIdx = bufferIndex + 1;
                                yield return lineBuffer.ToString();
                                lineBuffer = null;
                            }
                        }

                        previousIsLf = false;
                        break;
                    case '\r':
                        previousIsLf = true;
                        break;
                    default:
                        previousIsLf = false;
                        break;

                }


                bufferIndex++;
            } while (bufferIndex < charsRead);
            if (writeIdx < bufferIndex)
            {
                if (lineBuffer == null) lineBuffer = new StringBuilder();
                lineBuffer.Append(buffer, writeIdx, bufferIndex - writeIdx);
            }
        }
        //return last row
        if (lineBuffer != null && lineBuffer.Length > 0) yield return lineBuffer.ToString();
    }

C# Streamreader - 仅在 {CR}{LF} 处中断

C# Streamreader - Break on {CR}{LF} only

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