Getting error "Cannot perform the requested operation on an item that exists."

Getting error "Cannot perform the requested operation on an item that exists."

I have written the below method to create archive, but I found that it throws below error sometimes and sometimes it works well:
“Cannot perform the requested operation on an item that exists.
Type: Xceed.Zip.ZippedFile
Full Name: \Secured.html”

Stack Trace : at Xceed.FileSystem.AbstractFolder.CopyFilesTo(FileSystemEvents events, Object userData, AbstractFolder destinationFolder, Boolean recursive, Boolean replaceExistingFiles, Object[] filters)
at IdSecureLib.cXceedZip.CreateArchive(String sArchiveFileName, String sSourceFileName, CompressionLevel DefaultCompressionLevel, String sEncryptionPassword) in H:\NandKishore\A\core\IdSecureLib\IdSecureLib\cXceedZip.cs:line 244

I am using the these dll in my application:
1. Xceed.Compression (version 3.0.6173.0)
2. Xceed.Compression.Formats (version 3.0.6173.0)
3. Xceed.FileSystem (version 3.0.6173.0)
4. Xceed.Zip (version 3.0.6173.0)

Operating system : Windows 10.
Framework – dot net framework 2.0.

Parameters values in methods are:
sArchiveFileName = “C:\Users\nandkishore.sharma\AppData\Local\S\A\Secured.zip”
sSourceFileName = “C:\Users\nandkishore.sharma\AppData\Local\S\A\Secured”
DefaultCompressionLevel = Xceed.Compression.CompressionLevel.Normal
sEncryptionPassword = “”

public bool CreateArchive(string sArchiveFileName, string sSourceFileName, CompressionLevel DefaultCompressionLevel, string sEncryptionPassword)
{
bool bRet = false;
try
{
DiskFile oArchiveFile = new DiskFile(sArchiveFileName);
ZipArchive oZip = new ZipArchive(oArchiveFile);
ZipEvents oEvents = new ZipEvents();
oEvents.DiskRequired += new DiskRequiredEventHandler(oEvents_DiskRequired);
oEvents.ItemProgression += new ItemProgressionEventHandler(oEvents_ItemProgression);
oEvents.ByteProgression += new ByteProgressionEventHandler(oEvents_ByteProgression);
oZip.AllowSpanning = false;
oZip.DefaultCompressionLevel = DefaultCompressionLevel;
oZip.DefaultEncryptionPassword = sEncryptionPassword;
string sFolder = string.Empty;
string sFileName = string.Empty;
bool bRecursive = false;
if (File.Exists(sSourceFileName))
{
sFileName = Path.GetFileName(sSourceFileName);
sFolder = Path.GetDirectoryName(sSourceFileName);
}
else
{
sFileName = “*.*”;
sFolder = sSourceFileName;
bRecursive = true;
}
DiskFolder oFileParentFolder = new DiskFolder(sFolder);
oFileParentFolder.CopyFilesTo(oEvents, “Zipping”, oZip, bRecursive, false, sFileName);
if (oFileParentFolder != null)
{
oFileParentFolder = null;
}
if (oArchiveFile != null)
{
oArchiveFile = null;
}
if (oZip != null)
{
oZip = null;
}
if (oEvents != null)
{
oEvents = null;
}
bRet = true;
}
catch (Exception oEx)
{
oLogger.WriteLog(“CreateArchive()”, oEx.Message);
}
return bRet;
}

Please help me why I am getting error only sometimes.

Thanks in Advance.