FileUpload Control inside of grid View

I have a FileUpload control inside a ItemTemplate of GridView. Please see the image(http://prntscr.com/28tqz5)

At the end of form there is a save button. In button save click event i am looping through rows of GridView and finding FileUpload Control.

FileUpload fuCOA = (FileUpload)gvRow.FindControl("FileUpload4");
string fileName = fuCOA.FileName;

Problem is, i dont get the FileName..

There are not UpdatePanel used inside my page.

Please suggest.