Best way to handle null exceptions when concatenating a string in C#?

Question

I have this line of code that can throw null exceptions.

singleAddress.FullAddress = cc.MailingAddressStreet1.ToString() + " " +
   cc.MailingAddressCity.ToString() + " " +
   cc.MailingAddressState.ToString() + " " +
   cc.MailingAddressZip.ToString() + " " +
   cc.MailingAddressCountry.ToString();

I know that I can fix it by adding if statements to check if it is null. But is there a better recommended way to do it?

I just want to learn how to handle such exceptions better (and not have to write more code than I need to). Thanks in advance.

Well what do you want the result to be if any of these values is null? And what's the type of each value? (If it's already string, why are you calling ToString?) — Jon Skeet
– Jon Skeet, Commented Mar 5, 2012 at 17:48
Nothing. If someone did not provide a Country then the string should just not add anything. I didn't think about that When I wrote the question. Thanks for pointing that out. — Ammar
– Ammar, Commented Mar 5, 2012 at 18:01
no idea why I put the toString there. They were all string values. Sorry about the confusion. — Ammar
– Ammar, Commented Mar 5, 2012 at 18:18
Actually I realized that the .toString() was the reason why the exception was thrown out. I went back and removed all of them and the code worked fine. Now I know why you were asking about the toString :). Thanks @JonSkeet! — Ammar
– Ammar, Commented Mar 5, 2012 at 18:56

dtb · Accepted Answer · 2012-03-05 17:48:55Z

10

You can use the String.Join Method:

if (cc != null)
{
    singleAddress.FullAddress = string.Join(" ",
        cc.MailingAddressStreet1,
        cc.MailingAddressCity,
        cc.MailingAddressState,
        cc.MailingAddressZip,
        cc.MailingAddressCountry);
}

The String.Join Method takes a variable number of object arguments and calls the Object.ToString Method on each argument that is not null.

answered Mar 5, 2012 at 17:48

dtb

218k37 gold badges413 silver badges438 bronze badges

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

Comments

Phil · Accepted Answer · 2012-03-05 17:59:35Z

3

The String.Join method seems like a good way to go, but don't forget the null coalescing operator, e.g.

var s = (cc.MailingAddressStreet1 ?? string.Empty) + ...

I'm assuming that cc.MailingAddressStreet1 is already a string though.

This gives you the option of using an alternative string when the string is null, e.g.

var s = (cc.MailingAddressStreet1 ?? "(n/a)") + ...

And don't forget the brackets :)

answered Mar 5, 2012 at 17:59

Phil

43.2k9 gold badges102 silver badges102 bronze badges

Comments

Jon Skeet · Accepted Answer · 2012-03-05 18:03:37Z

3

I'd probably just use string.Format:

singleAddress.FullAddress = string.Format("{0} {1} {2} {3} {4}",
    cc.MailingAddressStreet1, cc.MailingAddressCity, cc.MailingAddressState,
    cc.MailingAddressZip, cc.MailingAddressCountry);

The NullReferenceExceptions were due to calling ToString - which will happen anyway for non-null values (even in your original code), and is pointless if the property types are already string...

answered Mar 5, 2012 at 18:03

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Comments

Matt Smucker · Accepted Answer · 2012-03-05 17:55:37Z

1

String.Concat should work

http://msdn.microsoft.com/en-us/library/system.string.concat.aspx

singleAddress.FullAddress = String.Concat(cc.MailingAddressStreet1.ToString(), 
                                        " ", cc.MailingAddressCity.ToString(), 
                                        " ", cc.MailingAddressState.ToString(),
                                        " ", cc.MailingAddressZip.ToString(),
                                        " ", cc.MailingAddressCountry.ToString());

answered Mar 5, 2012 at 17:55

Matt Smucker

5,2442 gold badges24 silver badges36 bronze badges

2 Comments

Ammar Over a year ago

I still got the nullReferenceException with this one because MailingAddressCountry was null. But thanks for telling me about Concat.

Ammar Over a year ago

Correction: It works if I remove the .toString. Sorry about that

Collectives™ on Stack Overflow

Best way to handle null exceptions when concatenating a string in C#?

4 Answers 4

Comments

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related