我有一个问题:如何在C#中从文本文件中删除一行?
我有一个问题:如何在C#中从文本文件中删除一行?
对于非常大的文件,我会采用以下方法
string tempFile = Path.GetTempFileName();
using(var sr = new StreamReader("file.txt"))
using(var sw = new StreamWriter(tempFile))
{
string line;
while((line = sr.ReadLine()) != null)
{
if(line != "removeme")
sw.WriteLine(line);
}
}
File.Delete("file.txt");
File.Move(tempFile, "file.txt");
更新我最初在2009年写过这篇文章,现在我认为通过使用LINQ和延迟执行可以实现上述功能。
var tempFile = Path.GetTempFileName();
var linesToKeep = File.ReadLines(fileName).Where(l => l != "removeme");
File.WriteAllLines(tempFile, linesToKeep);
File.Delete(fileName);
File.Move(tempFile, fileName);
上面的代码与第一个示例几乎完全相同,逐行读取并在内存中保留最少量的数据。
不过需要说明的是,由于我们在讨论文本文件,所以你很少需要使用磁盘作为中间存储介质。如果你没有处理非常大的日志文件,那么将内容读入内存而不必处理临时文件应该没有问题。
File.WriteAllLines(fileName,
File.ReadLines(fileName).Where(l => l != "removeme").ToList());
请注意,这里的.ToList
是至关重要的,可以强制立即执行。还要注意,所有的示例都假定文本文件是UTF-8编码。
读取文件,将行从内存中删除并将内容放回文件(覆盖)。如果文件很大,您可能希望逐行读取文件,并创建一个临时文件,稍后替换原始文件。
我同意John Saunders的观点,这并不是真正特定于C#的。然而,为了回答你的问题:你基本上需要重写文件。有两种方法可以做到这一点。
File.ReadAllLines
)List<string>
,然后删除该行)File.WriteAllLines
)- 可能需要使用ToArray
再次将List<string>
转换为字符串数组这意味着你必须知道你有足够的内存。另一个选择:
TextReader
/ TextWriter
,例如使用File.OpenText
和File.CreateText
)TextReader.ReadLine
) - 如果你不想删除它,请将其写入输出文件(TextWriter.WriteLine
)using
语句,这将自动发生)MORE +1 "sourcefilepath" > "targetFilePath"- Imran Amjad
List<string> quotelist=File.ReadAllLines(filename).ToList();
string firstItem= quotelist[0];
quotelist.RemoveAt(0);
File.WriteAllLines(filename, quotelist.ToArray());
return firstItem;
List<string> quotelist = new List<string>(File.ReadAllLines(filename));
- undefinedFile.WriteAllLines(filename, quotelist.ToArray());
- undefined我在马库斯·奥尔松的建议基础上进行了扩展,并编写了这个类,它添加了多个搜索字符串和一些事件:
public static class TextLineRemover
{
public static void RemoveTextLines(IList<string> linesToRemove, string filename, string tempFilename)
{
// Initial values
int lineNumber = 0;
int linesRemoved = 0;
DateTime startTime = DateTime.Now;
// Read file
using (var sr = new StreamReader(filename))
{
// Write new file
using (var sw = new StreamWriter(tempFilename))
{
// Read lines
string line;
while ((line = sr.ReadLine()) != null)
{
lineNumber++;
// Look for text to remove
if (!ContainsString(line, linesToRemove))
{
// Keep lines that does not match
sw.WriteLine(line);
}
else
{
// Ignore lines that DO match
linesRemoved++;
InvokeOnRemovedLine(new RemovedLineArgs { RemovedLine = line, RemovedLineNumber = lineNumber});
}
}
}
}
// Delete original file
File.Delete(filename);
// ... and put the temp file in its place.
File.Move(tempFilename, filename);
// Final calculations
DateTime endTime = DateTime.Now;
InvokeOnFinished(new FinishedArgs {LinesRemoved = linesRemoved, TotalLines = lineNumber, TotalTime = endTime.Subtract(startTime)});
}
private static bool ContainsString(string line, IEnumerable<string> linesToRemove)
{
foreach (var lineToRemove in linesToRemove)
{
if(line.Contains(lineToRemove))
return true;
}
return false;
}
public static event RemovedLine OnRemovedLine;
public static event Finished OnFinished;
public static void InvokeOnFinished(FinishedArgs args)
{
Finished handler = OnFinished;
if (handler != null) handler(null, args);
}
public static void InvokeOnRemovedLine(RemovedLineArgs args)
{
RemovedLine handler = OnRemovedLine;
if (handler != null) handler(null, args);
}
}
public delegate void Finished(object sender, FinishedArgs args);
public class FinishedArgs
{
public int TotalLines { get; set; }
public int LinesRemoved { get; set; }
public TimeSpan TotalTime { get; set; }
}
public delegate void RemovedLine(object sender, RemovedLineArgs args);
public class RemovedLineArgs
{
public string RemovedLine { get; set; }
public int RemovedLineNumber { get; set; }
}
使用方法:
TextLineRemover.OnRemovedLine += (o, removedLineArgs) => Console.WriteLine(string.Format("Removed \"{0}\" at line {1}", removedLineArgs.RemovedLine, removedLineArgs.RemovedLineNumber));
TextLineRemover.OnFinished += (o, finishedArgs) => Console.WriteLine(string.Format("{0} of {1} lines removed. Time used: {2}", finishedArgs.LinesRemoved, finishedArgs.TotalLines, finishedArgs.TotalTime.ToString()));
TextLineRemover.RemoveTextLines(new List<string> { "aaa", "bbb" }, fileName, fileName + ".tmp");
using System.IO
。void File_DeleteLine(int Line, string Path)
{
StringBuilder sb = new StringBuilder();
using (StreamReader sr = new StreamReader(Path))
{
int Countup = 0;
while (!sr.EndOfStream)
{
Countup++;
if (Countup != Line)
{
using (StringWriter sw = new StringWriter(sb))
{
sw.WriteLine(sr.ReadLine());
}
}
else
{
sr.ReadLine();
}
}
}
using (StreamWriter sw = new StreamWriter(Path))
{
sw.Write(sb.ToString());
}
}
我知道已经过了很长时间,但这对我非常有帮助,所以我想改进一下。来自Leonhard的答案对我非常有用。然而,如果您的文本文件像我的一样非常大,使用StringBuilder会导致OutOfMemory错误。因此,我是这样使用的:创建一个新文件并写入它。如果您愿意,可以删除第一个文件。请注意,Line变量确定将删除哪些行之前的文件。您可以修改它以指定要删除的行间隔。
void File_DeleteLine(int Line, string Path, string newPath)
{
StreamReader reader = new StreamReader(Path);
StreamWriter writer = new StreamWriter(newPath);
int Countup = 0;
while (!reader.EndOfStream)
{
Countup++;
if (Countup > Line)
{
writer.WriteLine(reader.ReadLine());
}
else
{
reader.ReadLine();
}
}
}
string fileIN = @"C:\myTextFile.txt";
string fileOUT = @"C:\myTextFile_Out.txt";
if (File.Exists(fileIN))
{
string[] data = File.ReadAllLines(fileIN);
foreach (string line in data)
if (!line.Equals("my line to remove"))
File.AppendAllText(fileOUT, line);
File.Delete(fileIN);
File.Move(fileOUT, fileIN);
}
从多个文件中删除一段代码块
为了补充@Markus Olsson的答案,我需要从多个文件中删除一段代码块。在核心项目中,我遇到了瑞典字符的问题,因此我需要安装System.Text.CodePagesEncodingProvider nuget包,并使用System.Text.Encoding.GetEncoding(1252)而不是System.Text.Encoding.UTF8。
public static void Main(string[] args)
{
try
{
var dir = @"C:\Test";
//Get all html and htm files
var files = DirSearch(dir);
foreach (var file in files)
{
RmCode(file);
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
throw;
}
}
private static void RmCode(string file)
{
string tempFile = Path.GetTempFileName();
using (var sr = new StreamReader(file, Encoding.UTF8))
using (var sw = new StreamWriter(new FileStream(tempFile, FileMode.Open, FileAccess.ReadWrite), Encoding.UTF8))
{
string line;
var startOfBadCode = "<div>";
var endOfBadCode = "</div>";
var deleteLine = false;
while ((line = sr.ReadLine()) != null)
{
if (line.Contains(startOfBadCode))
{
deleteLine = true;
}
if (!deleteLine)
{
sw.WriteLine(line);
}
if (line.Contains(endOfBadCode))
{
deleteLine = false;
}
}
}
File.Delete(file);
File.Move(tempFile, file);
}
private static List<String> DirSearch(string sDir)
{
List<String> files = new List<String>();
try
{
foreach (string f in Directory.GetFiles(sDir))
{
files.Add(f);
}
foreach (string d in Directory.GetDirectories(sDir))
{
files.AddRange(DirSearch(d));
}
}
catch (System.Exception excpt)
{
Console.WriteLine(excpt.Message);
}
return files.Where(s => s.EndsWith(".htm") || s.EndsWith(".html")).ToList();
}