upload image working in localhost , but on server not

Question

I have a site with upload image, on localhost working, but when I deploy it to server not working give me this error

 

Error! Object reference not set to an instance of an object

 

this is the method,

public string Createcontant(string articalname, string KEYWORD_NAME, string articalbody , HttpPostedFileBase file)
{
Contant c1 = new Contant() ;
OracleConnection conn = new OracleConnection();
OracleCommand cmd = new OracleCommand();
int MaxContentLength = 1024 * 1024 * 3; //3 MB
string[] AllowedFileExtensions = new string[] { ".jpg", ".gif", ".png", ".pdf" };
var fileName = Path.GetFileName(file.FileName);
var path = Path.Combine(HttpContext.Current.Server.MapPath("~/Images"), fileName);
file.SaveAs(path);
try
{
conn.ConnectionString = ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString;
cmd.Connection = conn;
conn.Open();
cmd.Parameters.AddWithValue("photo", fileName);
cmd.Parameters.AddWithValue("articalname", articalname);
cmd.Parameters.AddWithValue("KEYWORD_NAME", KEYWORD_NAME);
cmd.Parameters.AddWithValue("articalbody", articalbody);
cmd.Parameters.AddWithValue("parAddedUser", HttpContext.Current.Session["UserName"].ToString());
cmd.Parameters.AddWithValue("articalbody", articalbody);
string sql = "insert into contact" +
"( ARTICL_ID, ARTICAL_NAME, IDATE, IUSER," +
" KEYWORD_NAME, ARTICALBODY ,photo )" +
" Values " +
"( CONTANT_SEQ.nextval, :articalname,sysdate,:parAddedUser," +
" :KEYWORD_NAME,:articalbody , :photo)";
cmd.CommandText = sql;
cmd.ExecuteNonQuery();
cmd.Dispose();
cmd.Parameters.Clear();
return "done";
}

where is the problem?