Question

我有一个包含以下数据的txt文件：

:10FF800000040B4E00040B4E00047D1400047D148D
:10FF900000040B4E0004CF6200040B4E00040B4E15
:10FFA00000040B4E00040B4E00040B4E00040B4EDD
:10FFB00000047D1400047D1400047D1400047D14ED
:10FFC00000040B4E000000000000000000000000D4
:10FFD0000000000000040B4E0000000000000000C4
:10FFE0000000000000000000000000000000000011
:10FFF0000000000000000000060000000000BFF844
:020000020000FC
:020000040014E6
:043FF0005AC8A58C7A
:00000001FF

我想用C＃程序做的是在特定行之后或之前添加一行，让我们说添加一行：

:020000098723060

在此之前：

:020000020000FC

我尝试过使用File.ReadLines（＆＃34; file.txt＆＃34;）。Last（）;但这只是给了我最后一个，如果我想要第三个或第四个怎么办？还有，有没有办法确定＆＃34;：＆＃34;在文件？

Answer 1

最简单的方式 - 如果您乐意将整个文件读入内存 - 那就是：

public void InsertLineBefore(string file, string lineToFind, string lineToInsert)
{
    List<string> lines = File.ReadLines(file).ToList();
    int index = lines.IndexOf(lineToFind);
    // TODO: Validation (if index is -1, we couldn't find it)
    lines.Insert(index, lineToInsert);
    File.WriteAllLines(file, lines);
}

public void InsertLineAfter(string file, string lineToFind, string lineToInsert)
{
    List<string> lines = File.ReadLines(file).ToList();
    int index = lines.IndexOf(lineToFind);
    // TODO: Validation (if index is -1, we couldn't find it)
    lines.Insert(index + 1, lineToInsert);
    File.WriteAllLines(file, lines);
}

有很多高效方法可以做到这一点，但这种方法实际上是简单。

Answer 2

蛮力方法

string[] lines = File.ReadAllLines("file.txt");
using(StreamWrite sw = new StreamWriter("file.txt"))
{
   foreach(string line in lines)
   {
       if(line == ":020000020000FC")
          sw.WriteLine(":020000098723060");
       sw.WriteLine(line);
   }
}

Answer 3

我认为最好逐行读取和写入，特别是如果目标文件的大小往往很大：

using (StreamReader r = new StreamReader("Test.txt"))
{
    using (StreamWriter w = new StreamWriter("TestOut.txt"))
    {
        while (!r.EndOfStream)
        {
            string line = r.ReadLine();
            w.WriteLine(line);
            if (line == ":020000020000FC")
                w.WriteLine(":020000098723060");
        }
        w.Close();
        r.Close();
    }
}

Answer 4

不确定您是否因为尺寸等原因而试图避免读取整个文件...但是您不能只读取文件然后替换...例如。

var text = readFile(somePath);
writeFile( text.replace(":020000020000FC\n",":020000098723060\n:020000020000FC\n") , somePath);

Answer 5

这是一个解决方案，虽然它可能不是最好的，但确实有效：

public void AddTextToFile(string filePath, int lineNumber, string txt) //zero based lineNumber
{
        Collection<string> newLines = new Collection<string>(File.ReadAllLines(filePath).ToList());


        if (lineNumber < newLines.Count)
            newLines.Insert(lineNumber, txt);
        else 
            newLines.Add(txt);

        using (StreamWriter writer = new StreamWriter(filePath, false))
        {
            foreach (string s in newLines)
                writer.WriteLine(s);
        }
}

要回答关于确定字符串中是否存在“：”的问题，答案是肯定的，在上面的示例中，您可以检查该行是否包含它...

if(newLines[idx].Contains(':'))
//do something

Answer 6

“：”字符对实现没有任何帮助，这些行都已经 newline -delimited。

这是尝试一种方法，它不会将所有内容加载到内存或输出到其他文件。

永远不要越过溪流。

static Int32 GetCharPos(StreamReader s)
{
    var ia = BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField;
    Int32 charpos = (Int32)s.GetType().InvokeMember("charPos", ia, null, s, null);
    Int32 charlen = (Int32)s.GetType().InvokeMember("charLen", ia, null, s, null);
    return (Int32)s.BaseStream.Position - charlen + charpos;
}

static void Appsert(string data, string precedingEntry = null)
{
    if (precedingEntry == null)
    {
        using (var filestream = new FileStream(dataPath, FileMode.Append))
        using (var tw = new StreamWriter(filestream))
        {
            tw.WriteLine(data);
            return;
        }
    }

    int seekPos = -1;
    using (var readstream = new FileStream(dataPath, 
        FileMode.Open, FileAccess.Read, FileShare.Write))
    using (var writestream = new FileStream(dataPath, 
        FileMode.Open, FileAccess.Write, FileShare.Read))
    using (var tr = new StreamReader(readstream))
    {
        while (seekPos == -1)
        {
            var line = tr.ReadLine();
            if (line == precedingEntry)
                seekPos = GetCharPos(tr);
            else if (tr.EndOfStream)
                seekPos = (int)readstream.Length;
        }

        writestream.Seek(seekPos, SeekOrigin.Begin);
        readstream.Seek(seekPos, SeekOrigin.Begin);
        int readLength = 0;
        var readBuffer = new byte[4096];
        var writeBuffer = new byte[4096];
        var writeData = tr.CurrentEncoding.GetBytes(data + Environment.NewLine);
        int writeLength = writeData.Length;
        writeData.CopyTo(writeBuffer, 0);
        while (true & writeLength > 0)
        {
            readLength = readstream.Read(readBuffer, 0, readBuffer.Length);
            writestream.Write(writeBuffer, 0, writeLength);
            var tmp = writeBuffer;
            writeBuffer = readBuffer;
            writeLength = readLength;
            readBuffer = tmp;
        }                
    }
}

在文本文件中添加一行

6 个答案: