Context class - default!;

Question

I'm using an older version of .net to model creating property sets in the context class of a core 6 project. I notice in the core 6 project they include "= default!;" at the end.

having a hard time finding an explanation of the "= default!;" online. One explanation is a default value for a property, but this is a property set in a context class.

what is the = default!; in core 6 context class?

        public DbSet<Media.Models.Reference> Reference { get; set; } = default!;

Answer 1

There are a couple things going on.

Since C# 6 properties can be assigned an initial value.

The default literal sets default value of a type. For a C# class that means null.

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/default#default-literal

If you try to set the property to default without the "!" then you'll see a warning. "CS8625 - Cannot convert null literal to non-nullable reference type."

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings?f1url=%3FappId%3Droslyn%26k%3Dk(CS8625)

Adding the "!" (C# ! (null-forgiving) operator) overrides the warning.

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/null-forgiving