issue in extraction of zip file created using ionic.zip dll

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C#

C#4.0

Hi all,
I am facing the issue with my zip file ,when i try to open the file from zipped folder then it does not open ,but when i try to open file after extract the folder and then open ,it works fine ,please help me to resolve the issue,here is the function that i am using to zip with Ionic.Zip dll

private void ExportToZip()
       {
           Response.Clear();
           //Response.BufferOutput = false;
           Response.ContentType = "application/zip";
           Response.AddHeader("content-disposition", "filename=\"PnLBudgetExport.zip\"");
 
           using (ZipFile zip = new ZipFile())
           {
               if (Directory.Exists(Server.MapPath(ZIP_FOLDER)))
               {
                   foreach (string file in Directory.GetFiles(Server.MapPath(ZIP_FOLDER)))
                   {
                       zip.CompressionMethod = CompressionMethod.None;
                       //int indx = file.LastIndexOf("\\");
                       //zip.AddEntry(file.Substring(indx), File.ReadAllBytes(file));
                       zip.AddFile(file, string.Empty);
                   }
               }
 
               zip.Save(Response.OutputStream);
 

           }
           DeleteTempDir();
       }
 
where ZIP_FOLDER ="~/ZipExport"

Please help me ,Thanks in advance.