This is where Optioncomes in handy: val extractDateAsOptionInt = udf((d: String) => d match { case null => None case s => Some(s.substring(0, 10).filterNot(“-“.toSet).toInt) }) or to make it slightly more secure in general case: import scala.util.Try val extractDateAsOptionInt = udf((d: String) => Try( d.substring(0, 10).filterNot(“-“.toSet).toInt ).toOption) All credit goes to Dmitriy Selivanov who’ve pointed … Read more
Because that behavior follows established ternary logic where NULL is considered an unknown value. If you think of NULL as unknown, it becomes much more intuitive: Is unknown a equal to unknown b? There’s no way to know, so: unknown.
This should work: [XmlIgnore] public int? Age { get; set; } [XmlElement(“Age”)] public string AgeAsText { get { return (Age.HasValue) ? Age.ToString() : null; } set { Age = !string.IsNullOrEmpty(value) ? int.Parse(value) : default(int?); } }
int.TryParse is probably a tad easier: public static int? ToNullableInt(this string s) { int i; if (int.TryParse(s, out i)) return i; return null; } Edit @Glenn int.TryParse is “built into the framework”. It and int.Parse are the way to parse strings to ints.
In .NET 6, APIs were added to handle this, see this answer. Prior to this, you need to read the attributes yourself. This appears to work, at least on the types I’ve tested it with. public static bool IsNullable(PropertyInfo property) => IsNullableHelper(property.PropertyType, property.DeclaringType, property.CustomAttributes); public static bool IsNullable(FieldInfo field) => IsNullableHelper(field.FieldType, field.DeclaringType, field.CustomAttributes); public static … Read more
I got it to work with @Html.EditorFor(model => model.Foo) and then making a file at Views/Shared/EditorTemplates/Boolean.cshtml with the following: @model bool? @Html.CheckBox(“”, Model.GetValueOrDefault())
In C# 6 you can use the Null Conditional Operator. So the original test will be: int? value = objectA?.PropertyA?.PropertyB?.PropertyC;
Since DateTime is a struct, not a class, you get a DateTime object, not a reference, when you declare a field or variable of that type. And, in the same way as an int cannot be null, so this DateTime object can never be null, because it’s not a reference. Adding the question mark turns … Read more
According to the MSDN : Calling GetType on a Nullable type causes a boxing operation to be performed when the type is implicitly converted to Object. Therefore GetType always returns a Type object that represents the underlying type, not the Nullable type. When you box a nullable object, only the underlying type is boxed. Again, … Read more
The compiler is telling you that it doesn’t know how convert null into a DateTime. The solution is simple: DateTime? foo; foo = true ? (DateTime?)null : new DateTime(0); Note that Nullable<DateTime> can be written DateTime? which will save you a bunch of typing.