Class
- Data or Attributes
- state of the application
- Methods or Functions
- have behavior
Namespace
- is a container for related classes
Assembly (DLL or EXE)
- is a container for related namespaces
- is a file which can either be a EXE or a DLL
Application
- include one or more assemblies
Primitive Types (C# type)
- Integral Number
- byte (1byte, Max is 255)
- short
- int
- long
- Real Numbers
- float (4byte)
- double
- decimal
- Character
- char (2byte)
- Boolean
- bool (1byte)
- good practice
- Prefix Boolean names with is or has
- For example: isOver18, isCitizen, isEligible
Something tricky about real numbers
- data type is double by default
- wrong
float number = 1.2; decimal number = 1.2;
- right
float number = 1.2f; decimal number = 1.2m;
Non-Primitive Types
- String
- Array
- Enum
- Class
Overflowing
- for example
byte number = 255; number = number + 1; //0
- if you use check keyword, overflow will not happen and instead the program will throw an exception (But don‘t use it in real world )
Scope
- where a variable / constant has meaning
Type Conversion
- implicit type conversion
byte a = 1; int b = a;
- explicit type conversion (casting)
int c = 1; byte d = (byte)c;
- conversion between non-compatible types
string e = "100"; int f = int.Parse(e) var a = "1234"; int b = Convert.ToInt32(a);
C# Operators
- Arithmetic Operators
- +
- -
- *
- /
var a = 10; var b = 3; Console.WriteLine(a+b); // 3 Console.WriteLine((float)a / (float)b); // 3.333333
-
- %
- Postfix increment
int a = 1; int b = a++; //b = 1, a = 2;
-
- Prefix increment
int a = 1; int b = ++a; //b = 2, a = 2;
- Comparison Operators
- ==
- !=
- >
- >=
- <
- <=
- Assignment
- =
- +=
- -=
- *=
- /=
- Logical Operator
- &&
- And
- double ampersand
- a&&b
- ||
- Or
- double vertical line
- a||b
- !
- Not
- exclamation mark
- !a
- &&
- Bitwise Operators
- & And
- | Or
Comments
- Single-line Comment
// Here is a single-line comment
- Multi-line Comments
/* Here is a multi-line comment */
- When to use comments
- to explain whys, hows, constrains, etc
- Not explain the whats.
- comment do not explain what the code is doing
时间: 2024-10-08 10:35:15