When we have C# code interacting with the data base you run into this problem. Let me try and explain it. The database has nullable columns and C# has nullable types. For example, let us take a table Employee which has Id (int), name (string) and age (int). Let us assume that age will be null if no values are provided.
When you query the database for employee, the dataset or datareader will have DBNull for age. Now, this DBNull is not the same as C# null. This is the beginning of the problem. In order to make sure your code works properly, it has to expect that the reader can return a DBNull. You have to do the following in your code:
int? age = null;
age = (int)reader["Age"];
This code converts the DBNull to a C# null. The lack of common null types between the two makes code have two sets of defaults for data, one in the DB and the other in C#. Which can get confusing.
If you don't use nullable types due to performance, you have to invent your own null value:
int age = -1;
This conversion seems ugly and it is all over the code. Is there any other elegant solution to this?