title: converting documents to zip file, Added files and downloading, but while opening getting error
body: <ol>
  <li><p>Successfully adding documents in to zip add entry and downloading 
  it.</p></li>
  <li><p>But while opening for example Doc1, Doc2 If i download
         only doc1 (download and view Successfull)</p></li>
  <li><p>if i try doc2 it downloaded, but
         while opening(Cannot open file, It does not appear to be a valid
         archieve, Try again this is message when opened). If i checked both
        and downloaded and it's successfully downloaded and I can open it.</p></li>
  </ol>
  
  <p>Any help greatly appreciated</p>
  
  <pre><code>ZipFile zip = new ZipFile();
  
  foreach (GridDataItem item in RadGridSearchResults.MasterTableView.Items)
  {
      int documid;             
      bool chec;
      CheckBox check = (CheckBox)item.FindControl("CheckBox1");
      DocDetails dd = new DocDetails();
      if (check.Checked == true)
      {
          documid = Convert.ToInt32(item["DOCUMENT_ID"].Text);
          Document document = Document.GetDocumentByDocumentId(documid);    
          zip.AddEntry(document.DocumentName, document.DocumentFileImage);
  
      }                      
  }
  
  var zipMs = new MemoryStream();
  zip.Save(zipMs);
  
  byte[] fileData = zipMs.GetBuffer();           
  zipMs.Seek(0, SeekOrigin.Begin);
  zipMs.Flush();
  
  Response.Clear();
  Response.AddHeader("content-disposition", "attachment;filename=docs.zip ");
  Response.ContentType = "application/zip";
  Response.BinaryWrite(fileData);
  Response.End();
  </code></pre>