Is there a way to set my property as null or string.empty in order to restablish the field in the database as null. No. Because it’s non-nullable. If you want it to be nullable, you have to use Nullable<Guid> – if you didn’t, there’d be no point in having Nullable<T> to start with. You’ve got … Read more
EDIT: This has been confirmed as a bug in the compiler by the team. It is fixed in Roslyn. As a workaround, use a cast (int?)(–i) to stop the bug appearing, or don’t explicitly cast it to a Nullable<int> in the first place. The first code block generates the following in reflector: int? nullable3; int? … Read more
The reason why you shouldn’t always use nullable types is that sometimes you’re able to guarantee that a value will be initialized. And you should try to design your code so that this is the case as often as possible. If there is no way a value can possibly be uninitialized, then there is no … Read more
From Using Nullable Types (C# Programming Guide) (Link updated circa 2018) For an example of when you might use a nullable type, consider how an ordinary Boolean variable can have two values: true and false. There is no value that signifies “undefined”. In many programming applications, most notably database interactions, variables can exist in an … Read more
If you just want it to work, then perhaps: using System; using System.ComponentModel; using System.Xml.Serialization; public class Account { // your main property; TODO: your version [XmlIgnore] public Nullable<DateTime> AccountExpirationDate {get;set;} // this is a shim property that we use to provide the serialization [XmlAttribute(“AccountExpirationDate”)] [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)] public DateTime AccountExpirationDateSerialized { get {return AccountExpirationDate.Value;} set … Read more
Take a step back and think about the problem. You want a collection of widgets where the widget was ordered, or the widget was shipped, or the widget was processed. There are four possible states for your knowledge of “ordered”: this widget was ordered and I know that (true) this widget was not ordered and … Read more
Use the NULL-safe equal operator: SELECT * FROM A JOIN B ON A.C <=> B.C
var nums = new int?[] {1, null, 3}; var total = nums.Sum(); This relies on the IEnumerable<Nullable<Int32>>overload of the Enumerable.Sum Method, which behaves as you would expect. If you have a default-value that is not equal to zero, you can do: var total = nums.Sum(i => i.GetValueOrDefault(myDefaultValue)); or the shorthand: var total = nums.Sum(i => … Read more
The compiler requires that either the types of second and third operands are the same, or that one is implicitly convertible to the other. In your case, the types are DBNull and string, neither of which is implicitly convertible to the other. Casting either of them to object solves that. EDIT: Looks like it is … Read more
You can use the annotate() from django agrregation to do the trick: items = Item.objects.all().annotate(null_position=Count(‘position’)).order_by(‘-null_position’, ‘position’)