C# – Making a Non-nullable value type nullable

An easy to understand and simple solution.

// Save today's date.
var today = DateTime.Today;

// Calculate the age.
var age = today.Year - birthdate.Year;

// Go back to the year in which the person was born in case of a leap year
if (birthdate.Date > today.AddYears(-age)) age--;

However, this assumes you are looking for the western idea of the age and not using East Asian reckoning.

Change the return type to Nullable<T>, and call the method with the non nullable parameter

static void Main(string[] args)
{
    int? i = GetValueOrNull<int>(null, string.Empty);
}


public static Nullable<T> GetValueOrNull<T>(DbDataRecord reader, string columnName) where T : struct
{
    object columnValue = reader[columnName];

    if (!(columnValue is DBNull))
        return (T)columnValue;

    return null;
}