How to check if the LINQ expression does not come null

Question

I have this expression LINQ:

MaterialImage mainImage = images.First(i => i.IsMainImage == true);

My problem is that images. First(i => i.Ismainimage == true) can return null if you have no image with the property Ismainimage marked as true. What is the best way to check if null is given and use another equality to put a value on mainImage?

Answer 1

Utilize FirstOrDefault, if there is no return it returns the default value of the class that is null (This varies according to type, if it is a int for example the return is 0 as default value).

MaterialImage mainImage = images.FirstOrDefault(i => i.IsMainImage == true);
if (mainImage != null)
{ 
     // teve retorno;
}

That one Default of the method of Linnum is the same thing as default(T) and as has already been reported depending on the type it puts its default value.

For example:

using System;

public class Carros
{
    public int Id {get;set;}
}

public class Test
{
    public static void Main()
    {
        System.Console.WriteLine(default(int));
        System.Console.WriteLine(default(long));
        System.Console.WriteLine(default(DateTime));
        System.Console.WriteLine(default(Carros) == null);
    }
}

Exit:

0
0
1/1/0001 12:00:00 AM
True

Online Example

_References:

• Firstordefault - Linq
• Enumerable.Firstordefault Method
• Default Keyword in Generic Code (C# Programming Guide)
• default
• What is the use of default keyword in C#?