An exception of type 'System.NullReferenceException' occurred in Project_Portal.dll but was not handled in user code

Question

I'm loading Values from Session to Entity Object but is giving error. ( An exception of type 'System.NullReferenceException' occurred in Project_Portal.dll but was not handled in user code.Additional information: Object reference not set to an instance of an object. ). How can i resolve this Problem??? Here is my Code...

Here my form upload Files are converted to binary to save in database.So, i applied foreach loop for multiple files & load them one by one in List object.

 else if (ext.ToString().ToLower() == ".doc" || ext.ToString().ToLower() == 
 ".pdf")
                {
                    using (Stream fs = files[i].InputStream)
                    {
                        using (BinaryReader br = new BinaryReader(fs))
                        {
                            bytes = br.ReadBytes((Int32)fs.Length);

                        }
                    }
                    ProjectDataObject.Data = bytes;
                    ProjectDataObject.Nature = 3;
                }                    
                ProjectDataObject.EmailID = 
    HttpContext.Current.Session["EmailID"].ToString();
                ProjectDataObject.StudentProjectID 
    =Convert.ToInt32(HttpContext.Current.Session["StudentProjectID"]);
                DataList.Add(ProjectDataObject);
                foreach (ProjectDataEntity item in DataList)
                {
                    item.EmailID = ProjectDataObject.EmailID;
                    item.StudentProjectID = 
      ProjectDataObject.StudentProjectID;
                    item.Nature = ProjectDataObject.Nature;
                    item.Data = ProjectDataObject.Data;
                }

When i load EmailID from HttpContext.Current.Session["EmailID"].ToString() to ProjectDataObject.EmailID it generates the error shown above.