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This is a walkthrough of the new features with exercises included to practice using these features. This code was then subject to further compilation into CIL. Today the story is much simpler--only CIL is supported, and this code is cantidad de opciones sobre acciones modelo 720 from a new compiler. Now, you have fine-grained control over the scope of your variables.
Scopes can be started at the block level inside compound statementsin for statements, and in using statements as we will see below. There are several advantages to making scopes small. In this example, we declare the loop counter inside the 'for' statement in which it's used. The scope of the variable is the for statement itself, including the condition expression and the loop update parts.
If you attempt to do that, you will get the following. There's another place where scopes can be established: As a rule, when you use an IDisposable object, you should declare and instantiate it in a using statement.
The using statement calls the Dispose method on the object in the correct way, even if an exception occurs while you are calling methods on the object.
You can achieve the same result by putting the object inside a try block, and then explicitly calling Dispose in a finally block; in fact, this is how the using statement is translated by the compiler. Declarations can now be provided anywhere statements can be provided-- a declaration is syntactically a cantidad de opciones sobre acciones modelo 720, a declaration statement.
You can, therefore, provide declarations immediately prior to the usage. For instance, the following code will cause the compiler to issue the following diagnostic message: A local variable named 'i' cannot be declared in this scope because it would give a different meaning to 'i', which is already used in a parent or current scope to denote something else.
Static constructors are guaranteed to run before any static or instance calls are made to the class. Cantidad de opciones sobre acciones modelo 720 Cthe cantidad de opciones sobre acciones modelo 720 of static relates to the whole executing application domain. The static constructor has the following profile. A static constructor is used to initialize any static data, or to perform a particular action that needs to be performed only once.
No parameters can be provided for the static constructor, and it must be marked as static. Static fields are fields that are declared using the static keyword. Conceptually they apply to the class, not instances of the class. We'll show how a singleton, called instance in the example below, can be created by using the static constructor. The singleton will guarantee that only one instance of the class will ever be called, which is consumed by the following.
Cantidad de opciones sobre acciones modelo 720 now possible to assign a value to a field inline, i. This applies to both static and instance fields. In the following code, the values of field1 and field2 are defined in this fashion. However, using constants instead of defines has a number of benefits.
Macros that are defined in class scopes in class declarations are effectively available in all methods of all derived classes. This was originally a bug in the legacy compiler macro implementation, but this loophole is now massively exploited by application programmers.
This particular feature also considerably impacts compiler performance. Constants can be declared at the class level as suggested below. If you're in the scope of the class where the const is defined, you can omit the type name prefix MyClass in the example above. You can easily implement the concept of a macro library this way. The list of macro symbols becomes a class with public const definitions. The fleet application contains the FMDataHelper class that contains the following macro definitions.
You cantidad de opciones sobre acciones modelo 720 also define consts solely as variables. The compiler will maintain the invariant that the value can't be modified. Read-only fields can only be assigned a value once, and that value never changes; the field can be assigned its value either inline, at the place where the field is declared, or in the constructor.
Currently, that's the only difference between const and read-only. You can now declare a variable without explicitly providing the type of the variable, if the compiler can determine the type from the initialization expression. Note that the variable is still strongly-typed into one, unambiguous type. It's only possible to use var on declarations where an initialization expressions are provided from which the compiler will infer the type.
There are situations where this can make code easier to read, but this feature shouldn't be misused. You should consider the following rules:.
Previously, all member variables defined in a class were invariably protected. It's now possible to make the visibility of member variables explicit by adding the private, protected, and public keywords. The interpretation of these modifiers is obvious and aligns with the semantics for methods:. The default for member variables that aren't adorned with an explicit modifier is still protected. You should make it a habit of explicitly specifying the visibility.
As described, when a member variable is defined as public, it may be consumed outside of cantidad de opciones sobre acciones modelo 720 class in which it's defined. In this case, a qualifier designating the object hosting the variable has to be specified, using the dot notation as is the case for method calls. Reusing the code from above:. In this case, field1 is accessed using the explicit 'this. Making a member variable public may not be a good idea since it exposes the internal workings of the class to its consumers, creating a strong dependency between the class implementation and its consumers.
You should always strive to only depend on a contract, not an implementation. The semantics are the same as they are in C and other managed languages. The statements in the finally clause are executed when control leaves the try block, either normally or through an exception. The cantidad de opciones sobre acciones modelo 720 about what subscribes call was recorded on the publisher, which isn't useful in the environment.
It's now possible to provide Pre and Post handlers through code, by providing the SubscribesTo attribute on the subscribers. This example shows a publishing method called Publisher. The code shows how to access the variables, and the return values. This feature is provided for backward compatibility and, because the application code doesn't have many delegates, to publish important application events.
Pre and Post handlers can easily break as the result of added or removed parameters, changed parameter types, or because methods are no longer called, or called under different circumstances. Attributes are also used for binding event handlers to delegates:. Since the binding between the publisher and subscribers is done through attributes, there's no way of specifying the sequence in which subscribers are called.
The extension method feature lets you add extension methods to a target class by writing the methods in a separate extension class. The following rules apply:. It's perfectly valid to have private or protected static methods in an extension class. These are typically used for implementation details and are not exposed as extensions. The example below illustrates an extension class holding a few extension methods:.
The extension method technique doesn't affect the source code of the class it extends. Therefore, the addition to the class can be done without over-layering. Upgrades to the target class are never affected by any existing extension methods. However, if an upgrade to the target class adds a method that has the same name as your extension method, your extension method becomes unreachable through objects of the target class. Extension methods are easy to use.
The extension method technique uses the same dot-delimited syntax that you routinely use the call regular instance methods. Extension methods can access all public artifacts of the target class, but they can't access things that are protected or private. In this way, extension methods can be seen as a kind of syntactic sugar. Regardless of the target type, an extension class is used to add extension methods to the type.
For example, an extension table is not used to add methods to a table, and there's no such thing as an extension table. This is still possible, but you can now provide using clauses to make the use of such artifacts less onerous.
As opposed to a using statement, each using clause precedes the class in which the clause is applied. It's also possible to provide aliases that introduce a short name for a fully qualified name. Aliases can denote namespaces and classes as shown below.
This won't require you to rewrite any code, because the new type can express all of the values that the old one could. We provide this material in the interest of full disclosure only.
All instances of the real type are now implemented as instances of the. NET decimal type System. Just as the real type in previous versions, the decimal type in a binary coded decimal type that, unlike floating point type, is resilient to rounding errors. The range and resolution of the decimal type are different from the original types. The new real type doesn't eliminate the need for rounding. For example, the following code produces a result of 0. This is readily seen when using the debugger to show the value of the variables below.
The discrepancy obtained here cantidad de opciones sobre acciones modelo 720 due to the fact that only a finite number of decimals are provided. You should use the Round function to round to the number of decimals cantidad de opciones sobre acciones modelo 720. A decimal number is a floating-point value that consists of a sign, a numeric value where each digit in the value ranges from 0 to 9, and a scaling factor that indicates the position of a floating decimal point that separates the integral and fractional parts of the option strategy sell call and sell put value.