Question

I’m trying to get a property from an array of object that can be null (the array) and I’m always getting a null reference exception.

How can I tell LINQ to not process it in case it’s null or to return an empty string?

foreach (Candidate c in candidates) {
   results.Add(new Person 
      { 
         firstName = c.firstname, //ok
         lastName = c.Name, //ok

         // contactItems is an array of ContactItem
         // so it can be null that's why I get null exception 
         // when it's actually null
         phone = c.address.contactItems.Where( ci => ci.contactType == ContactType.PHONE).First().contactText 
      }
   );
}

I’ve also tried that to not take null. I don’t get the mechanism to tell LINQ not to process if the array is null.

phone = c.address.contactItems.Where( ci => ci != null && ci.contactType == ContactType.PHONE).First().contactText

Answer 1

You can check if it’s null with ?:(conditional) operator:

phone = c.address.contactItems == null ? ""
    : c.address.contactItems.Where( ci => ci.contactType == ContactType.PHONE).First().contactText 

If First throws an exception because there’s no one with ContactType.PHONE you can use DefaultIfEmpty with a custom default value:

c.address.contactItems.Where( ci => ci.contactType == ContactType.PHONE)
                      .DefaultIfEmpty(new Contact{contactText = ""})
                      .First().contactText 

Note that First now cannot throw an exception anymore since i’ve provided a default value.