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

Question

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

Answer 1

Not pretty, but I've had this for a while :

private string getNextFileName(string fileName)
{
    string extension = Path.GetExtension(fileName);

    int i = 0;
    while (File.Exists(fileName))
    {
        if (i == 0)
            fileName = fileName.Replace(extension, "(" + ++i + ")" + extension);
        else
            fileName = fileName.Replace("(" + i + ")" + extension, "(" + ++i + ")" + extension);
    }

    return fileName;
}

Assuming the files already exist:

• File.txt
• File(1).txt
• File(2).txt

the call getNextFileName("File.txt") will return "File(3).txt".

Not the most efficient because it doesn't use binary search, but should be ok for small file count. And it doesn't take race condition into account...