可空值類型與值類型這間的轉換

int s = 5;
int? s_null;
long t;
long? t_null;

t = s; //隱式轉換 S -> T
s = (int)t; //顯示轉換 T -> S

s_null = s; //隱式轉換 S -> S?
s = (int)s_null; //顯示轉換 S? -> T

t_null = s_null; //隱式轉換 S? -> T?
s_null = (int?)t_null; //顯示轉換 T? -> S?

t_null = s; //隱式轉換 S -> T?
s = (int)t_null; //顯示轉換 T? -> S