I tried zip all files in a folder, and save them to another folder.
Error:
That name specifies an existing directory. Please specify a filename. Parameter Name: fileName
AppConfig:
<appSettings>
    <add key="ZipLocation" value="c:\example\start"/>
    <add key="ZipSaveLocation" value="c:\example\extract"/>
</appSettings>
Code:
//using Ionic.Zip;
static void Main(string[] args)
{
    string startPath = ConfigurationManager.AppSettings["ZipLocation"].ToString();
    string zipPath = ConfigurationManager.AppSettings["ZipSaveLocation"].ToString();
    int key = Convert.ToInt32(Console.ReadLine());
    try
    {
        using (ZipFile zip = new ZipFile())
        {
            String[] filenames = System.IO.Directory.GetFiles(startPath);
            foreach (String filename in filenames)
            {
                Console.WriteLine("Adding {0}...", filename);
                ZipEntry e = zip.AddFile(filename);
                e.Comment = "bla bla."; 
            }
            zip.Comment = String.Format("This zip archive was created by the CreateZip example application on machine '{0}'", System.Net.Dns.GetHostName());
            zip.Save(zipPath);
        }
    }
    catch (Exception)
    {
        throw;
    }
}
				
                        
You have this:
and then you call this:
zipPath is not a file, it's a folder.
Fix your code by doing something like: