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Boxing is the operation of converting a value of a value type into a value of a corresponding reference type. [15] Boxing in C# is implicit. Unboxing is the operation of converting a value of a reference type (previously boxed) into a value of a value type. [15] Unboxing in C# requires an explicit type cast. Example:
In C#, apart from the distinction between value types and reference types, there is also a separate concept called reference variables. [3] A reference variable, once declared and bound, behaves as an alias of the original variable, but it can also be rebounded to another variable by using the reference assignment operator = ref. The variable ...
On the other hand, C# has no primitive wrapper classes, but allows boxing of any value type, returning a generic Object reference. In Objective-C, any primitive value can be prefixed by a @ to make an NSNumber out of it (e.g. @123 or @(123)). This allows for adding them in any of the standard collections, such as an NSArray.
Boxing is the operation of converting a value-type object into a value of a corresponding reference type. [108] Boxing in C# is implicit. Unboxing is the operation of converting a value of a reference type (previously boxed) into a value of a value type. [108] Unboxing in C# requires an explicit type cast. A boxed object of type T can only be ...
For a simple type like a number these conventions are relatively clear. Passing ByRef allows the procedure to modify the passed variable whereas passing ByVal does not. For an object, semantics can confuse programmers since an object is always treated as a reference. Passing an object ByVal copies the reference; not the state of the object. The ...
A parameter is an (unbound) variable, while the argument can be a literal or variable or more complex expression involving literals and variables. In case of call by value, what is passed to the function is the value of the argument – for example, f(2) and a = 2; f(a) are equivalent calls – while in call by reference, with a variable as ...
However, within C# value types, this has quite different semantics, being similar to an ordinary mutable variable reference, and can even occur on the left side of an assignment. One use of this in C# is to allow reference to an outer field variable within a method that contains a local variable that has the same name.
This is an accepted version of this page This is the latest accepted revision, reviewed on 12 February 2025. General-purpose programming language "C programming language" redirects here. For the book, see The C Programming Language. Not to be confused with C++ or C#. C Logotype used on the cover of the first edition of The C Programming Language Paradigm Multi-paradigm: imperative (procedural ...