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What does the ? indicate in the following C# code?
var handler = CallBack; handler?.Invoke(); I have read that you can use a ? before a type to indicate that it is a nullable type. Is this doing the same thing?
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If double question marks are uses it is to emphasise something in return, usually from the shock of the previous thing said. For example, if I said: 'My dog just died' (sad, but used for example...)
It's the null conditional operator. It basically means: "Evaluate the first operand; if that's null, stop, with a result of null. Otherwise, evaluate the second operand (as a member access of the first operand)."
It is used to define a default value for a nullable item (for both value types and reference types). It prevents the runtime InvalidOperationException exception.
It is a code style convention; it indicates that a method returns a boolean value (true or false) or an object to indicate a true value (or “truthy” value). The question mark is a valid character at the end of a method name. https://docs.ruby-lang.org/en/2.0.0/syntax/methods_rdoc.html#label-Method+Names.
This is C#6 code using the null conditional operator indicating that this code will not throw a NullReferenceException exception if handler is null:
Delegate handler = null; handler?.Invoke(); which avoid you writing null checks that you would have to do in previous versions of the C# language:
Delegate handler = null; if (handler != null) { handler.Invoke(); } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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