Index (zero based) must be greater than or equal to zero

Question

try

{

MXResumeWordDoc resumeWordDoc = new MXResumeWordDoc();

var IsResumeLoaded = resumeWordDoc.LoadResumeWordDocByDID(neo as Neo, applicationID);

if (IsResumeLoaded)

{

string fileExtension = System.IO.Path.GetExtension(resumeWordDoc.Elements.FileName.Value).ToLower();

string fileName = System.IO.Path.GetFileName(resumeWordDoc.Elements.FileName.Value).ToLower();

MemoryStream stream= new MemoryStream();

HttpResponse response1 = HttpContext.Current.Response;

response1.AddHeader("Content-Disposition", string.Format("attachment; filename=\"{0}.doc\""));

using (FileStream fs = new FileStream(fileName, FileMode.Create, System.IO.FileAccess.Write))

{

stream.WriteTo(fs);

}

response1.Flush();

response1.End();

}

response.Results.Add("response1");

}

catch (Exception ex)

{

neo.SendInformationalMXM("ResumeService", ex.Message, ex, this, "ResumeService.GetResume");

throw ex;

}

return response;

This code throwing Index (zero based) must be greater than or equal to zero and less than the size of the argument list. exception from the below line

response1.AddHeader("Content-Disposition", string.Format("attachment; filename=\"{0}.doc\""));

How to fix it?