How to access the file field control value in code behind

Below is my HTML View

 
   
    
      
          
     
    
  

In codebehind i tried to access the value like this

System.Web.UI.HtmlControls.HtmlInputFile FileUpload = pnleSMSBody.Content.FindControl("File1") as System.Web.UI.HtmlControls.HtmlInputFile;

i tried to find the uploaded file path like this  FileUpload.Value

but i am getting empty string vaule, please help me in solving this problem

 Thanks,

Siva