msdn c# code example
Example: c# ?
/*
A nullable value type T? represents all values of its underlying
value type T and an additional null value. For example, you can
assign any of the following three values to a bool? variable:
true, false, or null.
*/
double? pi = 3.14;
char? letter = 'a';
int m2 = 10;
int? m = m2;
bool? flag = null;