Introduction to C#


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Introduction to C#

  1. 1.  Variables Predefined Data Types Flow Control Enumerations Namespaces The Main() Method Compiling C# Files Console I/O C# Preprocessor Directives C# Programming Guidelines
  2. 2.  Syntax for Declaring a variable  [access-specifier] datatype variable_name;  Ex: int a; Initialization of Variables  Global variables has default values  Local variable must be explicitly initialized before use it.
  3. 3. • The scope of a variable is the region of code from which the variable can be accessed. ◦ The scope is determined by fallowing rules  A member variable of a class is in scope for as long as its containing class is in scope.  The local variable is in scope until closing brace indicates the end of the block.
  4. 4.  A constant variable is a variable whose value can not be changed throughout its life time. Syntax for Constants ◦ const datatype var_name=value; ◦ Constants have fallowing Characteristics  They must be initialized when they are declared and it can never be over written.  The value of a constant must be computable at compile time .
  5. 5.  Types of Data Types ◦ Value Types  Value types are stored in an area known as Stack ◦ Reference Types  Reference types stored in an area known as Managed Heap. ◦ CTS Types  The basic predefined types recognized by C# are not intrinsic to the language but are part of .NET Framework.
  6. 6.  Conditional Statements  When you use a conditional statement, you can specify a condition and one or more commands to be executed, depending on whether the condition is evaluated to true or false.  If, if-else, switch. Loops  The loop executes a statement or a block of statements repeatedly until a specified expression evaluates to false.  for, while, do-while, foreach.
  7. 7.  Jump Statements ◦ Branching is performed using jump statements, which cause an immediate transfer of the program control. ◦ The following keywords are used in jump statements:  break  return  continue  goto  throw
  8. 8.  An enumeration type (also named an enum) provides an efficient way to define a set of named integral constants that may be assigned to a variable. The enum keyword is used to declare an enumeration, a distinct type that consists of a set of named constants called the enumerator list. ◦ Ex: enum Days { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday }; //by default Sunday=0…Saturday=6 ◦ enum Months : byte { Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec }; By default the underlying type of each element in the enum is int. You can specify another integral numeric type by using a colon, as shown in the previous example. By default, the first enumerator has the value 0, and the value of each successive enumerator is increased by 1.
  9. 9.  Namespaces provide a way of organizing related classes and other types. The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way to create globally unique types. Syntax to create namespaces  namespace namespace_name { class class_name{…..} }
  10. 10.  using Directive The using directive has two uses: ◦ To allow the use of types in a namespace so that you do not have to qualify the use of a type in that namespace:  using System.Text; ◦ To create an alias for a namespace or a type. This is called a using alias directive.  using Project = PC.MyCompany.Project;
  11. 11.  The Main method is the entry point of a C# console application or windows application (Libraries and services do not require a Main method as an entry point). When the application is started, the Main method is the first method that is invoked. There can only be one entry point in a C# program. If you have more than one class that has a Main method, you must compile your program with the /main compiler option to specify which Main method to use as the entry point.
  12. 12.  Main must be static and it should not be public. Main can either have a void or int return type. The Main method can be declared with or without a string[] parameter that contains command-line arguments.
  13. 13.  The parameter of the Main method is a string array that represents the command-line arguments. ◦ static void Main(string[] args) {….} Usually you check for the existence of the arguments by testing the Length property. ◦ if (args.Length == 0) {//Inform user}
  14. 14.  Console class represents the standard input, output, and error streams for console applications. This class cannot be inherited. Some Methods in Console Class are ◦ Write() ◦ WriteLine() ◦ ReadLine() ◦ Clear() We can also set the position of the text in console
  15. 15.  Internal Comments ◦ C# uses traditional C-type single-line(//…) and Multiline (/*…………..*/) XML Documentation ◦ All XML comments begin with three forward slashes (///). The first two slashes signify a comment and tell the compiler to ignore the text that follows. The third slash tells the parser that this is an XML comment and should be handled appropriately. ◦ Ex: /// <summary> /// /// </summary> /// <param name="strFilePath"></param>
  16. 16.  The tags recognized by the compiler <c> The text you would like to indicate as code <code> Marks multiple lines as code <example> Marks up a code Example <include> Includes comments from another documentation file <list> Inserts a list into the documentation <param> Marks up a method parameter <value> Describes a property <summary> Provides a short summary of a type or member
  17. 17.  C# also includes a number of commands that are known as preprocessor directives. These commands never actually get translated to any commands in your executable code, but instead they affect aspects of compilation process.
  18. 18. #define Tells the compiler that a symbol with the given name exists.#undef Removes the definition of a symbol.#if, #elif, These directives inform the compiler whether to compile#else and a block of code#endif#warning These will respectively cause a warning or an error to beand #error raised when the compiler encounters them.#region and These are used to indicate that a certain block of code is#endregion to be treated as a single block#line This can be used to alter the filename and line number information that is output by the compiler in warning or error messages#pragma This can suppress or restore specific compiler warnings.
  19. 19.  Identifiers ◦ Identifiers are names you given to variables and user-defined types. Rules for Identifiers ◦ They must begin with a letter or underscore, although they can contain numeric characteristics ◦ You can’t use c# keywords as identifiers