CODEWITHSUNDEEP
c#
Mohan
Mohan

Reputation: 107

Object Reference Not set to instance of an object error while using FirstOrDefault

When I use this below code, I get object reference error, this might be because there is no match for "spider". My question is, How to check for null value in these situations

int fooID = foos.FirstOrDefault(f => f.Bar == "spider").ID;

I'm using this same scenario for different conditions for fetching different Items from the list like 

int fooID = foos.FirstOrDefault(f => f.Bar == "spider").ID; 
String fooDescription = foos.FirstOrDefault(f => f.Sides == "Cake").Description;

Is there any other way to check for null values.

Upvotes: 7

Views: 9132

Answers (2)

Trevor Pilley
Trevor Pilley

Reputation: 16393

The same way as you normally would, assign a variable and check it.

var foo = foos.FirstOrDefault(f => f.Bar == "spider");

if (foo != null)
{
    int fooID = foo.ID;
}

Based upon your updated example, you would need to do this instead:

var fooForId = foos.FirstOrDefault(f => f.Bar == "spider");
var fooForDescription = foos.FirstOrDefault(f => f.Sides == "Cake");

int fooId = fooForId != null ? fooForId.Id : 0;
string fooDescription = fooForDescription != null ? fooForDescription.Description : null; // or string.Empty or whatever you would want to use if there is no matching description.

Upvotes: 8

Ilya Ivanov
Ilya Ivanov

Reputation: 23626

You may also want to use DefaultIfEmpty extension method for bevaiour if there is no matching elements. Next code demonstrates the usage

string[] foos = {"tyto", "bar"};

var res = foos.Where(s => s.Length == 2)
              .DefaultIfEmpty("default")
              .First()
              .Length;

Console.WriteLine (res); //will print the length of default, which is 7

Upvotes: 1

Related Questions