nullable

I need to return values, and when someone asks for a value, tell them one of three things: Here is the value There is no value We have no information on this value (unknown) case 2 is subtly different than case 3. Example: val radio = car.radioType we know the value: return the radio type, say "pioneer" b. there is no value: return None c. we are missing data about this car, we don't know if it has a radio or not I thought I might extend scala's None and create an Unknown, but that doesn't seem possible. suggestions? thanks! Update: Ideally I'd like to be able to write code like this: car

I am puzzled by the following behavior of Nullable types: class TestClass { public int? value = 0; } TestClass test = new TestClass(); Now, Nullable.GetUnderlyingType(test.value) returns the underlying Nullable type, which is int . However, if I try to obtain the field type like this FieldInfo field = typeof(TestClass).GetFields(BindingFlags.Instance | BindingFlags.Public)[0]; and I invoke Nullable.GetUnderlyingType(field.FieldType).ToString() it returns a System.Nullable[System.Int32] type. So that means the method Nullable.GetUnderlyingType() has a different behavior depending on how you

I have the following code: private static LogLevel? _logLevel = null; public static LogLevel LogLevel { get { if (!_logLevel.HasValue) { _logLevel = readLogLevelFromFile(); } return _logLevel.Value; } } private static LogLevel readLogLevelFromFile() { ... } I get a ReSharper warning on the return statement about a possible System.InvalidOperationException and it suggests I check _logLevel to see if it is null first. However, readLogLevelFromFile returns LogLevel , not LogLevel? , so there is no way the return statement could be reached when _logLevel is null . Is this just an oversight by

I've hit a brickwall. My REST implementation won't accept Nullable values. [OperationContract] [WebInvoke(ResponseFormat = WebMessageFormat.Json, UriTemplate = "/Transactions?AccNo={AccNo}&CostCentreNo={CostCentreNo}&TransactionType={TransactionType}&Outstanding={Outstanding}&CheckStartDate={CheckStartDate}&CheckEndDate={CheckEndDate}")] List<Transactions> GetTransactions(Int32 AccNo, Int32 CostCentreNo, Int32 TransactionType, Boolean Outstanding, DateTime? CheckStartDate, DateTime? CheckEndDate); Whereas my original SOAP implementation does. So is there a way around this? Or do I have to re

Package has following package-info.java: @ParametersAreNonnullByDefault package foo; import javax.annotation.ParametersAreNonnullByDefault; Class has the following method: private static String toIsoString(@Nullable Instant dateTime) { return dateTime == null ? null : dateTime.toString(); } On which SonarQube (Version 6.2, SonarJava 4.14.0.11784) gives the following warning (squid:S2583): How can I convince SonarQube that the code is actually correct? Interestingly, SonarLint plugin (3.0.0.2041) in Idea doesn't generate the same warning. Apparently, this problem was caused by us using sonar

With these variables: Dim d1 As Date? = Nothing Dim d2 As DateTime? = Nothing Dim i1 As Integer? = Nothing Dim i2 As Int32? = Nothing Why am I allowed to do this?: Dim flag1 As Boolean = Date?.Equals(d1, d2) Dim flag2 As Boolean = Integer?.Equals(i1, i2) ...but not allowed to do this?: Dim flag3 As Boolean = DateTime?.Equals(d2, d1) Dim flag4 As Boolean = Int32?.Equals(i2, i1) The last code will fail with an error saying: The '?' character cannot be used here. VB.NET developers are not supposed to be using C# keywords (religion, you know). Seriously though, I agree with @Konrad this looks like

I'm trying to write an Extension method for nullable Enums. Like with this example: // ItemType is an enum ItemType? item; ... item.GetDescription(); So I wrote this method which doesn't compile for some reason that I don't understand: public static string GetDescription(this Enum? theEnum) { if (theEnum == null) return string.Empty; return GetDescriptionAttribute(theEnum); } I'm getting the following error on Enum? : only non-nullable value type could be underlying of system.nullable Why? Enum can not have the value null ! Update: If have lots of enums, ItemType is just an example of one of