Convert nullable bool? to bool

Question

You ultimately have to decide what the null bool will represent. If null should be false, you can do this:

bool newBool = x.HasValue ? x.Value : false;

Or:

bool newBool = x.HasValue && x.Value;

Or:

bool newBool = x ?? false;

You can use the null-coalescing operator: x ?? something, where something is a boolean value that you want to use if x is null.

Example:

bool? myBool = null;
bool newBool = myBool ?? false;

newBool will be false.

You can use Nullable{T} GetValueOrDefault() method. This will return false if null.

 bool? nullableBool = null;

 bool actualBool = nullableBool.GetValueOrDefault();

If you're going to use the bool? in an if statement, I find the easiest thing to do is to compare against either true or false.

bool? b = ...;

if (b == true) { Debug.WriteLine("true"; }
if (b == false) { Debug.WriteLine("false"; }
if (b != true) { Debug.WriteLine("false or null"; }
if (b != false) { Debug.WriteLine("true or null"; }

Of course, you can also compare against null as well.

bool? b = ...;

if (b == null) { Debug.WriteLine("null"; }
if (b != null) { Debug.WriteLine("true or false"; }
if (b.HasValue) { Debug.WriteLine("true or false"; }
//HasValue and != null will ALWAYS return the same value, so use whatever you like.

If you're going to convert it to a bool to pass on to other parts of the application, then the Null Coalesce operator is what you want.

bool? b = ...;
bool b2 = b ?? true; // null becomes true
b2 = b ?? false; // null becomes false

If you've already checked for null, and you just want the value, then access the Value property.

bool? b = ...;
if(b == null)
    throw new ArgumentNullException();
else
    SomeFunc(b.Value);

The easiest way is to use the null coalescing operator: ??

bool? x = ...;
if (x ?? true) { 

}

The ?? with nullable values works by examining the provided nullable expression. If the nullable expression has a value the it's value will be used else it will use the expression on the right of ??

bool? a = null;
bool b = Convert.toBoolean(a);