What does exclamation mark mean before invoking a method in C# 8.0? [duplicate]

Question

I have found a code written in C# seemingly version 8.0. In the code, there is an exclamation mark before invoking a method. What does this part of the code mean, and above all, what are its uses?

var foo = Entity!.DoSomething(); 

Answer 1

This would be the null forgiving operator.
It tells the compiler "this isn't null, trust me", so it does not issue a warning for a possible null reference.

In this particular case it tells the compiler that Entity isn't null.

Answer 2

! is the Null-Forgiving Operator. To be specific it has two main effects:

• it changes the type of the expression (in this case it modifies Entity) from a nullable type into a non-nullable type; (for example, object? becomes object)

• it suppresses nullability related warnings, which can hide other conversions

This seems to come up particularly with type parameters:

IEnumerable<object?>? maybeListOfMaybeItems = new object[] { 1, 2, 3 };  // inferred as IEnumerable<object?> var listOfMaybeItems = maybeListOfMaybeItems!;  // no warning given, because ! supresses nullability warnings IEnumerable<object> listOfItems = maybeListOfMaybeItems!;  // warning about the generic type change, since this line does not have ! IEnumerable<object> listOfItems2 = listOfMaybeItems;