How would you make a unique filename by adding a number?
c#, filenames, unique
Solution
Lots of good advice here. I ended up using a method written by Marc in 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:
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 :)
Problem
I would like to create a method which takes either a filename as a `string` or a `FileInfo` and 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. For example, if I have this FileInfo ``` var file = new FileInfo(@"C:\file.ext"); ``` I would like the method to give me a new FileInfo with C:\file 1.ext if C:\file.ext existed, and C:\file 2.ext if C:\file 1.ext existed and so on. Something like this: ``` 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. } ```