asp.net MVC 3 Error: "Object reference not set to an instance of an object" - asp.net-mvc

Question

i've a AccountController like this
public class AccountController : Controller
{
[Authorize]
public ActionResult MyProfile(string userEmail)
{
UserManager um = new UserManager();
UserProfile user = new UserProfile();
user = um.GetUserDetail(userEmail);
return View(user);
}
}
i've UserManager.cs Like this
public class UserManager
{
private ToLetDBEntities TLE = new ToLetDBEntities();
public UserProfile GetUserDetail(string uemail)
{
var userDetails = TLE.users.FirstOrDefault(x => x.email_add == uemail);
UserProfile up = new UserProfile();
up.cellno = userDetails.cellno.Trim();
up.email_add = userDetails.email_add.Trim();
up.name = userDetails.name.Trim();
up.password = userDetails.password.Trim();
return up;
}
}
When i'm debugging it gives error like
Object reference not set to an instance of an object
Null Reference Exception was Unhandled by User
At the line
up.cellno=userDetails.cellno.Trim();
Of the GetUserDetails function.

Answer 1

That error suggests that you don't have a userDetails instance, so you can't get the cellno property.
Are you sure that TLE.users.FirstOrDefault(x => x.email_add == uemail) is returning something? If you put a breakpoint on the line that gives you the error, then you can check what the value of userDetails is - it's probably null.

Answer 2

Most likely this query isn't returning anything:
TLE.users.FirstOrDefault(x => x.email_add == uemail);
The FirstOrDefault method won't give any kind of indication if no record is returned. The OrDefault part specifies this behavior. For any given return type, it will return the "default" for that type if no record is found.
For reference types (which yours is), the default is null. So this call would result in exactly that exception:
userDetails.cellno.Trim();
Since userDetails is null then it can't access a cellno property, hence the exception.
It's also possible in your case that userDetails isn't null but that the cellno property on it is. It's less likely, but possible. Looking at the runtime value while debugging would tell you if that's the case.
If userDetails is null, check your query conditions. Maybe the users collection has nothing in it? Maybe there are no records which match your x.email_add == uemail condition? (This is likely.)
If cellno is null then you'll want to check how that object is built, what the data in the database looks like, etc. Either way, you're not getting back the data you expect. The issue is in the data you're accessing.