Why does the Name Property of FileInfo object start with "~$"?

Question

So I'm writing some code that is going through a directory of .xlsx files and picking the file that was created last. It's a simple task, but there is something a bit strange happening with the Name property of a particular FileInfo object and potentially there are more cases of this occurring.

Here is my code:

        DirectoryInfo di = new DirectoryInfo(FolderPath);
        FileInfo[] FileArray = di.GetFiles("*.xlsx", SearchOption.AllDirectories);
        if (FileArray.Count() != 0) 
        {
            DateTime latestDate = DateTime.MinValue;
            string FileName = String.Empty;
            foreach (FileInfo File in FileArray)
            {
                if (File.CreationTime > latestDate)
                {
                    latestDate = File.CreationTime;
                    FileName = File.FullName;  
                }
            }
        }

The FileName is important because I use it to query the latest file for information and display it. However, the Name property of a particular .xlsx file (potentially more) is appearing like this ~$File.xlsx when in fact the file name is really File.xlsx. This causes the FullName property to contain these characters as well.

Is there any way to fix this? What triggers this?

Answer 1

Opening an xlsx file results in Excel creating a hidden file with the same name preceded by "~$". So if one of these Excel files are open at the time you retrieve the content of the directory, you will also get the temp file.

Add a filter that excludes hidden files and your issue is fixed.

Example:

FileAttributes attributes = File.GetAttributes(path);

if((attributes & FileAttributes.Hidden) == FileAttributes.Hidden)
{
    // Hidden file, just skip it
}

From http://msdn.microsoft.com/en-us/library/system.io.file.getattributes.aspx

Answer 2

~$ indicates that the file is a temporary file used by Microsoft Office. See here for additional information.