It’s worth noting that a generic HasFlag<T>(T thing, T flags) which is about 30 times faster than the Enum.HasFlag extension method can be written in about 30 lines of code. It can even be made into an extension method. Unfortunately, it’s not possible in C# to restrict such a method to only take things of … Read more
My question, however, is how the compiler enables a generic constraint to eliminate the need for boxing a value type that explicitly implements an interface. By “the compiler” it is not clear whether you mean the jitter or the C# compiler. The C# compiler does so by emitting the constrained prefix on the virtual call. … Read more
byte[] to Byte[] : byte[] bytes = …; Byte[] byteObject = ArrayUtils.toObject(bytes); Byte[] to byte[] : Byte[] byteObject = new Byte[0]; byte[] bytes = ArrayUtils.toPrimitive(byteObject);
Unboxing checks the exact type as explained in the documentation. Unboxing is an explicit conversion from the type object to a value type or from an interface type to a value type that implements the interface. An unboxing operation consists of: Checking the object instance to make sure that it is a boxed value of … Read more
The answer given (that there is no variance involving value types) is correct. The reason covariance and contravariance do not work when one of the varying type arguments is a value type is as follows. Suppose it did work and show how things go horribly wrong: Func<int> f1 = ()=>123; Func<object> f2 = f1; // … Read more
I first tought your question was a dupe of What code does the compiler generate for autoboxing? However, after your comment on @ElliottFrisch I realized it was different : I know the compiler behaves that way. I’m trying to figure out whether that behavior is guaranteed. For other readers, assume that “behaves that way” means … Read more
There are two things going on: 1) The compiler treats “null” not as a null reference but as a null value… the null value for whatever type it needs to convert to. In the case of a Nullable<T> it’s just the value which has False for the HasValue field/property. So if you have a variable … Read more
That’s a great question! Boxing occurs for exactly one reason: when we need a reference to a value type. Everything you listed falls into this rule. For example since object is a reference type, casting a value type to object requires a reference to a value type, which causes boxing. If you wish to list … Read more
Finding the most specific method is defined in a very formal way in the Java Language Specificaion (JLS). I have extracted below the main items that apply while trying to remove the formal formulae as much as possible. In summary the main items that apply to your questions are: JLS 15.12.2: your use case falls … Read more
Boxing refers to a conversion of a non-nullable-value type into a reference type or the conversion of a value type to some interface that it implements (say int to IComparable<int>). Further, the conversion of an underlying value type to a nullable type is also a boxing conversion. (Caveat: Most discussions of this subject will ignore … Read more