C# Object reference not set to an instance of an object

Question

I have the following code:

public void SetUser(User user)
{
   string streetNumber = "";

   if (user.Address.StreetNo != null)
      streetNumber = user.Address.StreetNo.ToString();
   else
     streetNumber = "";
}

I get the ever popular

Object reference not set to an instance of an object.

issue.

First check if user is not null then user.Address not null and only then StreeNo... — Darius Kucinskas
– Darius Kucinskas, Commented Aug 19, 2011 at 8:21
where does the stacktrace point you to? are you sure that "user" will not be null? Sorry but I can't tell from your code. It might be the Address of the user is null it might be the StreeetNo - it might be almost everything in there — Random Dev
– Random Dev, Commented Aug 19, 2011 at 8:22
Thanks for the comments guys, they were write and go along with the answer curt has provided. The Stack did show the user exsisted but I wasn't doing the check. — Anicho
– Anicho, Commented Aug 19, 2011 at 9:09

vvvvv · Accepted Answer · 2022-03-15 10:59:22Z

3

public void SetUser(User user)
{
   string streetNumber = "";

   if (user != null && user.Address != null && user.Address.StreetNo != null) {
      streetNumber = user.Address.StreetNo.ToString();
   }
}

Taking into account @CKoenig's suggestion, the following throws an exception if the user or user.Address are null:

public void SetUser(User user)
{

   if (user == null) {
       throw new System.ArgumentNullException("user", "user cannot be null");
   }

   if (user.Address == null) {
       throw new System.ArgumentNullException("Address", "Address cannot be null");
   }
   
   string streetNumber = "";

   if (user.Address.StreetNo != null) {
      streetNumber = user.Address.StreetNo.ToString();
   }
}

edited Mar 15, 2022 at 10:59

vvvvv

32.9k19 gold badges70 silver badges103 bronze badges

answered Aug 19, 2011 at 8:22

Curtis

104k69 gold badges280 silver badges359 bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

Random Dev Over a year ago

I would recommend throwing if either is null - the method is named "SetUser" if it can't because there is nothing to set it should not pretent to do.

user47589 Over a year ago

The method name has to be wrong. It doesn't do anything like the method body describes.

Curtis Over a year ago

@Inuyasha OP could have simplified their method leaving only this part which seems to be throwing an exception

cdhowie Over a year ago

@Curt: I suggest using ArgumentNullException at least for the case where user is null, since this is a more specific exception type.

sll Over a year ago

@Curt : you still throwing an exception when user != null, does this make any sense?

|

cdhowie · Accepted Answer · 2011-08-19 08:22:06Z

2

Either user is null, or user.Address is null. You need to test them too.

answered Aug 19, 2011 at 8:22

cdhowie

172k25 gold badges303 silver badges324 bronze badges

3 Comments

cdhowie Over a year ago

No, you missed this clause: if (user.Address.StreetNo != null). He is already checking if user.Address.StreetNo is null. The problem is that this test itself will throw the exception if either of user or user.Address are null.

Random Dev Over a year ago

so sorry- you are right ... better think first ... but alas then there will be 10 answers ;)

Anicho Over a year ago

Thanks guys +1 because you were right accepted curts because he provided code with answer.

sll · Accepted Answer · 2011-08-19 08:25:12Z

2

public void SetUser(User user) 
{    
   string streetNumber = String.Empty;     

   if (user!= null 
       && user.Address != null 
       && user.Address.StreetNo != null)       
   {
         streetNumber = user.Address.StreetNo.ToString();    
   }
}

answered Aug 19, 2011 at 8:25

sll

62.7k22 gold badges109 silver badges157 bronze badges

Comments

Random Dev · Accepted Answer · 2011-08-19 08:23:20Z

1

Check your stacktrace and:

user
user.Address
user.Address.StreetNo

with an if ... == null then ...

answered Aug 19, 2011 at 8:23

Random Dev

52.4k9 gold badges95 silver badges120 bronze badges

Comments

k06a · Accepted Answer · 2011-08-19 08:25:01Z

1

if (user != null
    && user.Address != null
    && user.Address.StreetNo != null)
{
    // ...
}

answered Aug 19, 2011 at 8:25

k06a

19k10 gold badges75 silver badges112 bronze badges

Collectives™ on Stack Overflow

C# Object reference not set to an instance of an object

5 Answers 5

10 Comments

3 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

10 Comments

3 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related