Web Forms :: How To Open File In New Browser

I am using following code for opening file in file dialog model.

FileStream fs;
String strFileName = @"C:My ExternalFile Path";
fs = File.Open(strFileName, FileMode.Open);
Byte[] buffer = new byte[1048576];
long bytBytes = fs.Length;
fs.Read(buffer, 0, 1048576);
fs.Close();
Response.AddHeader("Content-disposition", "attachment; filename=" + strFileName);
Response.ContentType = "application/octet-stream";
Response.BinaryWrite(buffer);
Response.End();

When click on open button the file is opening in same window, but i want to open in new window.