![Identifiers and Variables
• Identifiers refer to the name of the variables,
functions, arrays, classes etc created by
programmer
• The only allowed characters for identifiers are all
alphanumeric characters([A-Z], [a-z], [0-9]), ‘_‘
(underscore). For example “geek@” is not a valid
C# identifier as it contain ‘@’ – special character.
• Identifiers should not start with digits([0-9]). For
example “123geeks” is a not a valid in C#
identifier.
• Identifiers should not contain white spaces.](https://image.slidesharecdn.com/unit1chapter3-210813053044/85/C-Basics-6-320.jpg)
![Example
• using System;
namespace TypeConversionApplication {
class ExplicitConversion {
static void Main(string[] args) {
double d = 5673.74;
int i; // cast double to int.
i = (int)d;
Console.WriteLine(i);
Console.ReadKey();
} } }](https://image.slidesharecdn.com/unit1chapter3-210813053044/85/C-Basics-18-320.jpg)
C# Basics
- 1. UNIT 1 Chapter 3 C# Basics
- 2. Introduction • Microsoft developed • C# is a simple, modern, object oriented and type safe programming language derived from C and C++.
- 3. Comparing C# with java • Same as Garbage collector • Both are tend to intermediate language. C#- MSIL , Java –byte code • C# contains more primitive data types than java • Both supports for multidimensional arrays.,multiple class inheritance
- 4. Comparing C# with C++ • C++ is C#’s closet relative • C# code does not require header files. All codes written in inline • The C# types are different from C++ • C# statements are quite similar to C++ statements
- 5. Features of C# • Simplicity • Consistent Behaviour • Modern Programming Language • Pure Object Oriented Programming Language • Type Safety • Feature of Versioning • Compatible with other Language • Inter-operability
- 6. Identifiers and Variables • Identifiers refer to the name of the variables, functions, arrays, classes etc created by programmer • The only allowed characters for identifiers are all alphanumeric characters([A-Z], [a-z], [0-9]), ‘_‘ (underscore). For example “geek@” is not a valid C# identifier as it contain ‘@’ – special character. • Identifiers should not start with digits([0-9]). For example “123geeks” is a not a valid in C# identifier. • Identifiers should not contain white spaces.
- 7. Identifiers and Variables • Identifiers are not allowed to use as keyword unless they include @ as a prefix. For example, @as is a valid identifier, but “as” is not because it is a keyword. • C# identifiers allow Unicode Characters. • C# identifiers are case-sensitive. • C# identifiers cannot contain more than 512 characters. • Identifiers does not contain two consecutive underscores in its name because such types of identifiers are used for the implementation.
- 9. Data Types
- 10. Value types • The value data types are integer-based and floating-point based. C# language supports both signed and unsigned literals. • There are 2 types of value data type in C# language. 1.Predefined Data Types - such as Integer, Boolean, Float, etc. • 2) User defined Data Types - such as Structure, Enumerations, etc. • The memory size of data types may change according to 32 or 64 bit operating system.
- 11. Value types • Example int x=10; Int y=x; y=20; //after this stmt x holds value 10 and y holds value 20
- 12. Reference Types • The reference data types do not contain the actual data stored in a variable, but they contain a reference to the variables. • If the data is changed by one of the variables, the other variable automatically reflects this change in value. • There are 2 types of reference data type in C# language. • 1) Predefined Types - such as Objects, String. • 2) User defined Types - such as Classes, Interface.
- 13. Reference Types • Class Demo { class XYZ { public int myValue; } public static void main() { XYZ X = new XYZ(); X.myValue = 10; XYZ Z=X; Z.myValue = 20; //after this stmt both X.myvalue and Z.myvalue equal to 20 } }
- 14. Pointers • The pointer in C# language is a variable, it is also known as locator or indicator that points to an address of a value.
- 15. Pointers • Symbols: & (ampersand sign) - Address operator - Determine the address of a variable. * (asterisk sign) - Indirection operator - Access the value of an address.
- 16. Declaring a pointer • The pointer in C# language can be declared using * (asterisk symbol). • int * a; //pointer to int • char * c; //pointer to char
- 17. Type Conversion • Type conversion is converting one type of data to another type. It is also known as Type Casting. In C#, type casting has two forms − • Implicit type conversion − These conversions are performed by C# in a type-safe manner. For example, are conversions from smaller to larger integral types and conversions from derived classes to base classes. • Explicit type conversion − These conversions are done explicitly by users using the pre-defined functions. Explicit conversions require a cast operator.
- 18. Example • using System; namespace TypeConversionApplication { class ExplicitConversion { static void Main(string[] args) { double d = 5673.74; int i; // cast double to int. i = (int)d; Console.WriteLine(i); Console.ReadKey(); } } }
- 19. Convert Class • Convert base data type to another base data type • Convert.ToInt16(val) - Val converted to short • Convert.ToInt32(val) - Val converted to int • Convert.ToChar(val) - Val converted to char • Convert.ToString(val) - Val converted to string
- 20. Parse Function • It converts a string containing a number to numeric • Sbyte.Parse(str) - convert str string representation of number in sbyte • byte.Parse(str) - convert str string representation of number in byte
- 21. Boxing • Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. • When the common language runtime (CLR) boxes a value type, it wraps the value inside a System.Object instance and stores it on the managed heap. • Boxing is implicit;
- 22. Boxing • Boxing is used to store value types in the garbage-collected heap. Boxing is an implicit conversion of a value type to the type object or to any interface type implemented by this value type. Boxing a value type allocates an object instance on the heap and copies the value into the new object.
- 23. Boxing
- 24. example • In the following example, the integer variable i is boxed and assigned to object o. • int i = 123; // The following line boxes i. object o = i;
- 25. UnBoxing • Unboxing extracts the value type from the object. • unboxing is explicit. • The concept of boxing and unboxing underlies the C# unified view of the type system in which a value of any type can be treated as an object.
- 26. UnBoxing • Unboxing is an explicit conversion from the type object to a value type or from an interface type to a value type that implements the interface. An unboxing operation consists of: • Checking the object instance to make sure that it is a boxed value of the given value type. • Copying the value from the instance into the value-type variable.
- 27. UnBoxing
- 28. example • The object o can then be unboxed and assigned to integer variable i: o = 123; i = (int)o; // unboxing