An elegant way of renaming a file if it already exists when archiving

Question

I'd like to write an archiving function that takes all files in a folder and move them into an archive sub folder using the current date. The process could be run several times in a day and therefore needs to handle duplicates.

The rules for the archiving are below:

1. If a file name already exists, I'd like to add an underscore "_" and a number (starting from 1).
2. If the file name has already been modified the I'd like to increment the number.

I can do this using lots of File.Exist and LastIndexOf calls but is there a more elegant way? maybe with LINQ?

EDIT:

This is the code I have already. It's a bit rough and ready but it gives an idea of what I want to do.

/// <summary>
/// Move the local file into the archive location.
/// If the file already exists then add a counter to the file name or increment the existing counter
/// </summary>
/// <param name="LocalFilePath">The full path of the file to be archived</param>
/// <param name="ArchiveFilePath">The proposed full path of the file once it's been archived</param>
private void ArchiveFile(string LocalFilePath, string ArchiveFilePath)
{
    // Ensure the file name doesn't already exists in the location we want to move it to
    if (File.Exists(ArchiveFilePath) == true)
    {
        // Does the archive file have a number at the end?
        string[] archiveSplit = Path.GetFileNameWithoutExtension(ArchiveFilePath).Split('_');
        if( archiveSplit.Length == 1)
        {
            // No number detected so append the number 1 to the filename
            string newArcFileName = string.Format("{0}_1.{1}",
                Path.GetFileNameWithoutExtension(ArchiveFilePath), Path.GetExtension(ArchiveFilePath));

            // Create the new full path
            string newArcPath = Path.Combine(Path.GetDirectoryName(ArchiveFilePath), newArcFileName);

            // recursively call the archive folder to ensure the new file name doesn't exist before moving
            ArchiveFile( LocalFilePath, newArcPath);
        }
        else
        {
            // Get the number of the last element of the split
            int lastNum = Convert.ToInt32( archiveSplit.Last().Substring(1) ) +1;

            // Rebuild the filename using the incremented number
            string newArcFileName = archiveSplit[0];
            for (int i = 1; i < archiveSplit.Length; i++)
            {
                newArcFileName += archiveSplit[i];
            }
            // finally add the number and extension
            newArcFileName = string.Format("{0}_{1}.{2}", newArcFileName, lastNum, Path.GetExtension(ArchiveFilePath));

            // Create the new full path
            string newArcPath = Path.Combine(Path.GetDirectoryName(ArchiveFilePath), newArcFileName);

            // recursively call the archive folder to ensure the new file name doesn't exist before moving
            ArchiveFile(LocalFilePath, newArcPath);
        }
    }
    else
    {
        // There is no file with a matching name
        File.Move(LocalFilePath, ArchiveFilePath);
    }
}

Answer 1

The Directory class has a method to receive a list of all files within. That method allows you to specify a filter string, like so:

Directory.GetFiles(directoryPath, filterString);

If you already know your filename prefix, you can use that filter string to get all the files within that pattern:

filterString = string.Format("{0}_*.{1}", defaultFileNameWithoutExtension, defaultExtension);

You can then simply select the one with the highest suffix, extract the suffix digits, increase it and build your new (unused) file name.

Disclaimer: This was written by heart, feel free to edit in case of errors :)

Answer 2

File.Exists would still need to be called even if you use LINQ, that will not change.

I suggest keeping things simple - looping with File.Exists and LastIndexOf is a suitable solution, unless performance is imperative.

Answer 3

Maybe, you should use the "Path" API and use EndsWith instead of LastIndexOf :).

You can also have a file wich store the tree of files. (Took an eye to rsync)

Do you really want to make several duplicates of the same files even if it doesn't change ? Are you looking for an updated "modified datetime" ?

http://msdn.microsoft.com/en-us/library/system.io.path.aspx : Path