Rewrite HasValue to the ?? Operators

Question

Is it safe to rewrite the following code:

bool b = foo.bar.HasValue ? foo.bar.Value : false;

to

bool b = foo.bar.Value ?? false;

where bar is the nullable type bool?

Answer 1

The easiest fix there is

bool b = foo.bar.GetValueOrDefault();

which is also actually cheaper than .Value as it omits the has-value check. It will default to default(T) , which is indeed false here (it just returns the value of the underlying T field, without any checks at all).

If you need a different default to default(T), then:

var value = yourNullable.GetValueOrDefault(yourPreferredValue);

Answer 2

What you want is:

bool b = foo.bar ?? false;

This is (surprisingly) safe and an intended use for the null-coalescing operator.

The ?? operator is called the null-coalescing operator and is used to define a default value for a nullable value types as well as reference types. It returns the left-hand operand if it is not null; otherwise it returns the right operand.

Source: http://msdn.microsoft.com/en-us/library/ms173224.aspx

In the case of Nullable<T>, it is functionally equivalent to Nullable<T>.GetValueOrDefault(T defaultValue).

The code:

bool b = foo.bar.Value ?? false;

Will cause a compiler-error, because you cannot apply the operator to value types, and Nullable<T>.Value always returns a value-type (or throws an exception when there is no value).