Concepts of nullable.
Nullables - C# have a fantastic data types which is called as NULLABLE.Here you can assign range of values as well as null values.
Example int? dnf1 = null;
int? dnf2 = 100;
double? dnf3 = new double?();
double? dnf4 = 1.18;
bool? dnf5 = new bool?();
Console.WriteLine(dnf1, dnf2,dnf3, dnf4);
Console.WriteLine("Nullable", dnf5);
Output
,100, ,1.16