Variable type ending with ?

Question

What does ? mean:

public bool? Verbose { get; set; }

When applied to string?, there is an error:

Answer 1

The ? operator indicates that the property is in fact a nullable type.

public bool? Verbose { get; set; } 

is equilvalent to

public Nullable Verbose { get; set; }

A nullable type is a special type introduced in c# 2.0 which accepts a value type as a generic praramater type and allow nulls to be assigned to the type.

The nullable type only accept value types as generic arguments which is why you get a compile error when you try to use the ? operator in conjunction with the string type.

For more information: MSDN Nullable Types