C#：如何通过添加数字来创建唯一的文件名？

C#: How would you make a unique filename by adding a number?

提问by Svish

I would like to create a method which takes either a filename as a stringor a FileInfoand adds an incremented number to the filename if the file exists. But can't quite wrap my head around how to do this in a good way.

我想创建一个方法，它将文件名作为 astring或 aFileInfo并在文件存在时向文件名添加一个递增的数字。但是我无法完全理解如何以一种好的方式做到这一点。

For example, if I have this FileInfo

例如，如果我有这个 FileInfo

var file = new FileInfo(@"C:\file.ext");

I would like the method to give me a new FileInfo with C:\file 1.extif C:\file.extexisted, and C:\file 2.extif C:\file 1.extexisted and so on. Something like this:

我想的方法给我一个新的FileInfo C：\文件1.ext如果C：\ file.ext存在，C：\文件2.ext如果C：\文件1.ext存在等。像这样的东西：

public FileInfo MakeUnique(FileInfo fileInfo)
{
    if(fileInfo == null)
        throw new ArgumentNullException("fileInfo");
    if(!fileInfo.Exists)
        return fileInfo;

    // Somehow construct new filename from the one we have, test it, 
    // then do it again if necessary.
}

采纳答案by Svish

Lots of good advice here. I ended up using a method written by Marcin an answer to a different question. Reformatted it a tiny bit and added another method to make it a bit easier to use "from the outside". Here is the result:

这里有很多很好的建议。最后我用书面的方法马克在回答不同的问题。稍微重新格式化并添加了另一种方法，使其更容易“从外部”使用。结果如下：

private static string numberPattern = " ({0})";

public static string NextAvailableFilename(string path)
{
    // Short-cut if already available
    if (!File.Exists(path))
        return path;

    // If path has extension then insert the number pattern just before the extension and return next filename
    if (Path.HasExtension(path))
        return GetNextFilename(path.Insert(path.LastIndexOf(Path.GetExtension(path)), numberPattern));

    // Otherwise just append the pattern to the path and return next filename
    return GetNextFilename(path + numberPattern);
}

private static string GetNextFilename(string pattern)
{
    string tmp = string.Format(pattern, 1);
    if (tmp == pattern)
        throw new ArgumentException("The pattern must include an index place-holder", "pattern");

    if (!File.Exists(tmp))
        return tmp; // short-circuit if no matches

    int min = 1, max = 2; // min is inclusive, max is exclusive/untested

    while (File.Exists(string.Format(pattern, max)))
    {
        min = max;
        max *= 2;
    }

    while (max != min + 1)
    {
        int pivot = (max + min) / 2;
        if (File.Exists(string.Format(pattern, pivot)))
            min = pivot;
        else
            max = pivot;
    }

    return string.Format(pattern, max);
}

Only partially tested it so far, but will update if I find any bugs with it. (Marcs code works nicely!) If you find any problems with it, please comment or edit or something :)

到目前为止只对它进行了部分测试，但如果我发现它有任何错误，我会更新。（Marc的代码运行良好！）如果您发现它有任何问题，请评论或编辑或其他内容:)

回答by unwind

This is just a string operation; find the location in the filename string where you want to insert the number, and re-construct a new string with the number inserted. To make it re-usable, you might want to look fora number in that location, and parse it out into an integer, so you can increment it.

这只是一个字符串操作；在文件名字符串中找到要插入数字的位置，并重新构造一个插入数字的新字符串。为了使其可重复使用，您可能希望在该位置查找一个数字，并将其解析为一个整数，以便您可以递增它。

Please note that this in general this way of generating a unique filename is insecure; there are obvious race conditionhazards.

请注意，这种生成唯一文件名的方式通常是不安全的；存在明显的竞争条件风险。

There might be ready-made solutions for this in the platform, I'm not up to speed with C# so I can't help there.

平台中可能有现成的解决方案，我没有跟上 C# 的速度，所以我无能为力。

回答by Steve Guidi

Take a look at the methods in the Pathclass, specifically Path.GetFileNameWithoutExtension(), and Path.GetExtension().

查看Path类中的方法，特别是Path.GetFileNameWithoutExtension()和Path.GetExtension()。

You may even find Path.GetRandomFileName()useful!

您甚至可能会发现Path.GetRandomFileName()很有用！

Edit:

编辑：

In the past, I've used the technique of attempting to write the file (with my desired name), and then using the above functions to create a new name if an appropriate IOExceptionis thrown, repeating until successful.

过去，我使用了尝试写入文件（使用我想要的名称）的技术，然后如果IOException抛出适当的名称，则使用上述函数创建一个新名称，重复直到成功。

回答by Mehrdad Afshari

public FileInfo MakeUnique(string path)
{            
    string dir = Path.GetDirectoryName(path);
    string fileName = Path.GetFileNameWithoutExtension(path);
    string fileExt = Path.GetExtension(path);

    for (int i = 1; ;++i) {
        if (!File.Exists(path))
            return new FileInfo(path);

        path = Path.Combine(dir, fileName + " " + i + fileExt);
    }
}

Obviously, this is vulnerable to race conditions as noted in other answers.

显然，正如其他答案中所述，这很容易受到竞争条件的影响。

回答by mga911

If checking if the file exists is too hard you can always just add a date and time to the file name to make it unique:

如果检查文件是否存在太难了，您可以随时向文件名添加日期和时间以使其唯一：

FileName.YYYYMMDD.HHMMSS

文件名.YYYYMMDD.HHMMSS

Maybe even add milliseconds if necessary.

如有必要，甚至可以添加毫秒。

回答by TheVillageIdiot

If the format doesn't bother you then you can call:

如果格式不打扰您，那么您可以调用：

try{
    string tempFile=System.IO.Path.GetTempFileName();
    string file=System.IO.Path.GetFileName(tempFile);
    //use file
    System.IO.File.Delete(tempFile);
}catch(IOException ioe){
  //handle 
}catch(FileIOPermission fp){
  //handle
}

PS:- Please read more about this at msdnbefore using.

PS：-请在使用前在msdn 上阅读更多相关信息。

回答by Daniel Earwicker

Insert a new GUID into the file name.

在文件名中插入一个新的 GUID。

回答by lc.

The idea is to get a list of the existing files, parse out the numbers, then make the next highest one.

这个想法是获取现有文件的列表，解析出数字，然后制作下一个最高的数字。

Note: This is vulnerable to race conditions, so if you have more than one thread creating these files, be careful.

注意：这很容易受到竞争条件的影响，因此如果您有多个线程创建这些文件，请小心。

Note 2: This is untested.

注 2：这是未经测试的。

public static FileInfo GetNextUniqueFile(string path)
{
    //if the given file doesn't exist, we're done
    if(!File.Exists(path))
        return new FileInfo(path);

    //split the path into parts
    string dirName = Path.GetDirectoryName(path);
    string fileName = Path.GetFileNameWithoutExtension(path);
    string fileExt = Path.GetExtension(path);

    //get the directory
    DirectoryInfo dir = new DirectoryInfo(dir);

    //get the list of existing files for this name and extension
    var existingFiles = dir.GetFiles(Path.ChangeExtension(fileName + " *", fileExt);

    //get the number strings from the existing files
    var NumberStrings = from file in existingFiles
                        select Path.GetFileNameWithoutExtension(file.Name)
                            .Remove(0, fileName.Length /*we remove the space too*/);

    //find the highest existing number
    int highestNumber = 0;

    foreach(var numberString in NumberStrings)
    {
        int tempNum;
        if(Int32.TryParse(numberString, out tempnum) && tempNum > highestNumber)
            highestNumber = tempNum;
    }

    //make the new FileInfo object
    string newFileName = fileName + " " + (highestNumber + 1).ToString();
    newFileName = Path.ChangeExtension(fileName, fileExt);

    return new FileInfo(Path.Combine(dirName, newFileName));
}

回答by Michael Stum

/// <summary>
/// Create a unique filename for the given filename
/// </summary>
/// <param name="filename">A full filename, e.g., C:\temp\myfile.tmp</param>
/// <returns>A filename like C:\temp\myfile633822247336197902.tmp</returns>
public string GetUniqueFilename(string filename)
{
    string basename = Path.Combine(Path.GetDirectoryName(filename),
                                   Path.GetFileNameWithoutExtension(filename));
    string uniquefilename = string.Format("{0}{1}{2}",
                                            basename,
                                            DateTime.Now.Ticks,
                                            Path.GetExtension(filename));
    // Thread.Sleep(1); // To really prevent collisions, but usually not needed
    return uniquefilename;
}

As DateTime.Ticks has a resolution of 100 nanoseconds, collisions are extremely unlikely. However, a Thread.Sleep(1) will ensure that, but I doubt that it's needed

由于DateTime.Ticks 的分辨率为 100 纳秒，因此极不可能发生冲突。然而，一个 Thread.Sleep(1) 将确保，但我怀疑它是必要的

回答by Handcraftsman

Instead of poking the disk a number of times to find out if it has a particular variant of the desired file name, you could ask for the list of files that already exist and find the first gap according to your algorithm.

您可以询问已存在的文件列表并根据您的算法找到第一个间隙，而不是多次戳磁盘以找出它是否具有所需文件名的特定变体。

public static class FileInfoExtensions
{
    public static FileInfo MakeUnique(this FileInfo fileInfo)
    {
        if (fileInfo == null)
        {
            throw new ArgumentNullException("fileInfo");
        }

        string newfileName = new FileUtilities().GetNextFileName(fileInfo.FullName);
        return new FileInfo(newfileName);
    }
}

public class FileUtilities
{
    public string GetNextFileName(string fullFileName)
    {
        if (fullFileName == null)
        {
            throw new ArgumentNullException("fullFileName");
        }

        if (!File.Exists(fullFileName))
        {
            return fullFileName;
        }
        string baseFileName = Path.GetFileNameWithoutExtension(fullFileName);
        string ext = Path.GetExtension(fullFileName);

        string filePath = Path.GetDirectoryName(fullFileName);
        var numbersUsed = Directory.GetFiles(filePath, baseFileName + "*" + ext)
            .Select(x => Path.GetFileNameWithoutExtension(x).Substring(baseFileName.Length))
            .Select(x =>
                    {
                        int result;
                        return Int32.TryParse(x, out result) ? result : 0;
                    })
            .Distinct()
            .OrderBy(x => x)
            .ToList();

        var firstGap = numbersUsed
            .Select((x, i) => new { Index = i, Item = x })
            .FirstOrDefault(x => x.Index != x.Item);
        int numberToUse = firstGap != null ? firstGap.Item : numbersUsed.Count;
        return Path.Combine(filePath, baseFileName) + numberToUse + ext;
    }
}