// Type: double?, selector function is called
public static int Test6g()
{
Data_Ndouble[] source = new Data_Ndouble[]{ new Data_Ndouble{name="Tim", num=9.5},
new Data_Ndouble{name="John", num=null},
new Data_Ndouble{name="Bob", num=8.5}
};
double? expected = 18.0;
var actual = source.Sum((e) => e.num);
return ((expected == actual) ? 0 : 1);
}
