Professional C# 6 and .NET Core 1.0. Christian Nagel
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Название: Professional C# 6 and .NET Core 1.0

Автор: Christian Nagel

Издательство: John Wiley & Sons Limited

Жанр: Зарубежная образовательная литература

Серия:

isbn: 9781119096634

isbn:

СКАЧАТЬ for names of constants. This is not advised in C# because such names are harder to read – the convention is to use Pascal casing throughout:

      The only other casing convention that you are advised to use is camel casing. Camel casing is similar to Pascal casing, except that the first letter of the first word in the name is not capitalized: employeeSalary, confirmationDialog, plainTextEncoding. Following are three situations in which you are advised to use camel casing:

      • For names of all private member fields in types:

      Note, however, that often it is conventional to prefix names of member fields with an underscore:

      • For names of all parameters passed to methods:

      • To distinguish items that would otherwise have the same name. A common example is when a property wraps around a field:

      If you are wrapping a property around a field, you should always use camel casing for the private member and Pascal casing for the public or protected member, so that other classes that use your code see only names in Pascal case (except for parameter names).

      You should also be wary about case sensitivity. C# is case sensitive, so it is syntactically correct for names in C# to differ only by the case, as in the previous examples. However, bear in mind that your assemblies might at some point be called from Visual Basic applications – and Visual Basic is not case sensitive. Hence, if you do use names that differ only by case, it is important to do so only in situations in which both names will never be seen outside your assembly. (The previous example qualifies as okay because camel case is used with the name that is attached to a private variable.) Otherwise, you may prevent other code written in Visual Basic from being able to use your assembly correctly.

      Name Styles

      Be consistent about your style of names. For example, if one of the methods in a class is called ShowConfirmationDialog, then you should not give another method a name such as ShowDialogWarning or WarningDialogShow. The other method should be called ShowWarningDialog.

      Namespace Names

      It is particularly important to choose Namespace names carefully to avoid the risk of ending up with the same name for one of your namespaces as someone else uses. Remember, namespace names are the only way that .NET distinguishes names of objects in shared assemblies. Therefore, if you use the same namespace name for your software package as another package, and both packages are used by the same program, problems will occur. Because of this, it’s almost always a good idea to create a top-level namespace with the name of your company and then nest successive namespaces that narrow down the technology, group, or department you are working in or the name of the package for which your classes are intended. Microsoft recommends namespace names that begin with <CompanyName>.<TechnologyName>, as in these two examples:

      Names and Keywords

      It is important that the names do not clash with any keywords. In fact, if you attempt to name an item in your code with a word that happens to be a C# keyword, you’ll almost certainly get a syntax error because the compiler will assume that the name refers to a statement. However, because of the possibility that your classes will be accessed by code written in other languages, it is also important that you don’t use names that are keywords in other .NET languages. Generally speaking, C++ keywords are similar to C# keywords, so confusion with C++ is unlikely, and those commonly encountered keywords that are unique to Visual C++ tend to start with two underscore characters. As with C#, C++ keywords are spelled in lowercase, so if you hold to the convention of naming your public classes and members with Pascal-style names, they will always have at least one uppercase letter in their names, and there will be no risk of clashes with C++ keywords. However, you are more likely to have problems with Visual Basic, which has many more keywords than C# does, and being non-case-sensitive means that you cannot rely on Pascal-style names for your classes and methods.

      Check the MSDN documentation at http://msdn.microsoft.com/library. In Development Tools and Languages, C# reference, you find a long list of C# keywords that you shouldn’t use with classes and members. Also check the list of Visual Basic keywords if Visual Basic could be used as a language accessing your classes.

      Use of Properties and Methods

      One area that can cause confusion regarding a class is whether a particular quantity should be represented by a property or a method. The rules are not hard and fast, but in general you should use a property if something should look and behave like a variable. (If you’re not sure what a property is, see Chapter 3.) This means, among other things, that

      • Client code should be able to read its value. Write-only properties are not recommended, so, for example, use a SetPassword method, not a write-only Password property.

      • Reading the value should not take too long. The fact that something is a property usually suggests that reading it will be relatively quick.

      • Reading the value should not have any observable and unexpected side effect. Furthermore, setting the value of a property should not have any side effect that is not directly related to the property. Setting the width of a dialog has the obvious effect of changing the appearance of the dialog on the screen. That’s fine, because that’s obviously related to the property in question.

      • It should be possible to set properties in any order. In particular, it is not good practice when setting a property to throw an exception because another related property has not yet been set. For example, to use a class that accesses a database, you need to set ConnectionString, UserName, and Password, and then the author of the class should ensure that the class is implemented such that users can set them in any order.

      • Successive reads of a property should give the same result. If the value of a property is likely to change unpredictably, you should code it as a method instead. Speed, in a class that monitors the motion of an automobile, is not a good candidate for a property. Use a GetSpeed method here; but Weight and EngineSize are good candidates for properties because they will not change for a given object.

      If the item you are coding satisfies all the preceding criteria, it is probably a good candidate for a property. Otherwise, you should use a method.

      Use of Fields

      The guidelines are pretty simple here. Fields should almost always be private, although in some cases it may be acceptable for constant or read-only fields to be public. Making a field public may hinder your ability to extend or modify the class in the future.

      The previous guidelines should give you a foundation of good practices, and you should use them in conjunction with a good object-oriented programming style.

      A final helpful note to keep in mind is that Microsoft has been relatively careful about being consistent and has followed its own guidelines when writing the .NET base classes, so a very good way to get an intuitive feel for the conventions to follow when writing .NET code is to simply look at the base classes – see how classes, members, and namespaces are named, and how the class hierarchy works. Consistency between the base classes and your classes will facilitate readability and maintainability.

Summary

      This СКАЧАТЬ