Namespaces & Preprocessor Version 1.0 C# .Net Software Development

Overview Namespaces using Statement Pre-Processor Directives Copyright © 2008 by Dennis A. Fairclough all rights reserved.

Namespace Namespaces provide a hierarchical means of organizing C# programs and libraries. Namespaces contain types and other namespaces—for example, the System namespace contains a number of types, such as the Console class referenced in the program, and a number of other namespaces, such as IO and Collections. A using directive that references a given namespace enables unqualified use of the types that are members of that namespace. Copyright © 2008 by Dennis A. Fairclough all rights reserved.

Namespace A organizational scoping construct. Can be organized Standalone Nested Declarations in a C# program define the constituent elements of the program. C# programs are organized using namespaces (§‎9), which can contain type declarations and nested namespace declarations. Are open ended (duplicates are merged) Namespaces and types that have no enclosing namespace are members of the global namespace. Copyright © 2008 by Dennis A. Fairclough all rights reserved.

Namespaces Namespaces have no access restrictions. It is not possible to declare private, protected, or internal namespaces, and namespace names are always publicly accessible. Can use “using” statement or the fully qualified namespace. The using directive can use an “Alias” name. using-alias-directive: using identifier = namespace-or-type-name; Copyright © 2008 by Dennis A. Fairclough all rights reserved.

using Statement using <namespace>; using <ident> = <namespace>; Copyright © 2008 by Dennis A. Fairclough all rights reserved.

Pre-Processing Directives #define and #undef, which are used to define and undefine, respectively, conditional compilation symbols (§‎2.5.3). #if, #elif, #else, and #endif, which are used to conditionally skip sections of source code (§‎2.5.4). #line, which is used to control line numbers emitted for errors and warnings (§‎2.5.7). #error and #warning, which are used to issue errors and warnings, respectively (§‎2.5.5). #region and #endregion, which are used to explicitly mark sections of source code (§‎2.5.6). Copyright © 2008 by Dennis A. Fairclough all rights reserved.

Pre-Processing Directives A pre-processing directive always occupies a separate line of source code and always begins with a # character and a pre-processing directive name. White space may occur before the # character and between the # character and the directive name. A source line containing a #define, #undef, #if, #elif, #else, #endif, or #line directive may end with a single-line comment. Delimited comments (the /* */ style of comments) are not permitted on source lines containing pre-processing directives. Copyright © 2008 by Dennis A. Fairclough all rights reserved.

Pre-Processing Directives Pre-processing directives are not tokens and are not part of the syntactic grammar of C#. However, pre-processing directives can be used to include or exclude sequences of tokens and can in that way affect the meaning of a C# program. Copyright © 2008 by Dennis A. Fairclough all rights reserved.

What did you learn? ?? Copyright © 2008 by Dennis A. Fairclough all rights reserved.