how to resolve object Null error? - asp.net

Question

I have a situation where i am assigning some value to a session. I have a situation in which that code is calling repeatedly. some times this code throws error of object null. I am not getting why this is happening while i am assign value to it.My code is
if (HttpContext.Current.Cache["Cache"] == null)
{
CreateChanhe();
DataTable dtcache= HttpContext.Current.Cache["HNS Connection"] as DataTable; //CreateConnectString(CCMMUtility.Encryptdata(txtPin.Text));
string sqlFilter = "Sp = '" + classses.DecryptString(HttpContext.Current.Request.Cookies["Cookies"].Values["sp"].ToString(), classses.SP) + "'";
DataRow[] dr = dtcache.Select(sqlFilter);
if (dr.Length > 0)
{
String[] Con = new String[2];
Con[0] = dr[0][0].ToString();
Con[1] = dr[0][1].ToString();
sp= Con[1];
HttpContext.Current.Session["Name"] = dr[0][2].ToString();
}
}
When i am try to do "Add watch" while debugging its says the "value" has some value but the HttpContext.Current.Session["Name"] is null. Can some let me know why this is happening.
Actually i am creating a cache then fills session from that cache. this is based on my requirement.

Answer 1

I suspect that dr[0][2] is null so when you call .ToString() on it you are getting a NRE.

Answer 2

Is that the HttpContext.Current is null? If so wrap a null check around it like this:
if (HttpContext.Current != null)
{
if (HttpContext.Current.Cache["Cache"] == null)
{
CreateChanhe();
DataTable dtcache= HttpContext.Current.Cache["HNS Connection"] as DataTable; //CreateConnectString(CCMMUtility.Encryptdata(txtPin.Text));
string sqlFilter = "Sp = '" + classses.DecryptString(HttpContext.Current.Request.Cookies["Cookies"].Values["sp"].ToString(), classses.SP) + "'";
DataRow[] dr = dtcache.Select(sqlFilter);
if (dr.Length > 0)
{
String[] Con = new String[2];
Con[0] = dr[0][0].ToString();
Con[1] = dr[0][1].ToString();
sp= Con[1];
HttpContext.Current.Session["Name"] = dr[0][2].ToString();
}
}
}