How to open file in new browser

Hi
I am using following code for opening file in file dialog model.
FileStream fs;
String strFileName = @"C:\My External\File 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.
 
Please provide suitable code/suggestion.
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