"2017-2-19" C # data type, data conversion, variables, constants, escape characters

Data type

I. Basic data types

1. Value type ( NOT null)

⑴ integral type (can be negative)

Byle,int,short,long (from small to large)

Common integral type

int a= value (less than 10 digits)

Long b= value (more than 10 digits)

⑵ floating-point type ( can be negative and integer )

float f=25.6f; (uppercase and lowercase, if an integer can be removed f)

Double d=25.6;

Decimal dm=25.6m; (both uppercase and lowercase)

Common floating-point type

Double,decimal

2. Boolean type

BOOL type can only be true or false

BOOL Ok=true/false;

3. Character type

Char (only one character, length must be 1) can be a number, letter, text, symbol

Char c= ' ★ '; (single quote required)

Ii. type of reference

1. String

String can be null

2. Time-Date datetime

DateTime dt=new datetime (int year, int month, int day);

DateTime riqi=new datetime (2017,2,19);

Datetme Now=datetime.now; (Show system Current time)

Data conversion

1. Implicit conversion (boxing)

Change the value type to a reference type, and do not declare the conversion mode;

            string " Ten " ;             int  - ;             string c = a + b;            Console.Write (c);            Console.ReadLine ();

The display is 1020;

String c=a is not valid and cannot be converted directly;

The addition of other types to string types is assimilated by string;

2. Explicit conversions, also known as casts (unboxing)

1. Use the parse;

The target type. Parse (variable/value);

String a = "10";

int B=int. Parse (a);

Console.ReadLine ();

2. Use ();

(target type) variable/value

3. Using Convert; (recommended)

Convert.to target Type (variable/value)

string a ="ten"; int b =convert. ToInt32 (a); Console.ReadLine ();

Convert.tobyte (a);

Convert.tosingle (a);

Convert.todecimal (a);

Convert.todouble (a);

Convert.toboolean (a);

Convert.todatetime (a);

Other types are converted to String types: variable/value. ToString ();

Escape character: \

\ can cancel the special meaning of the next symbol

\ ' single quotation mark \ ' quotation mark \ \ Backslash \a warning (generates beep) \b Backspace \f page break \ n line break \ r enter \ t horizontal tab \v vertical tab

Constants: const can only be assigned one time

Keyword before variable name (cannot be assigned, only value)

Exercises

Console.Write ("Please enter the first Student's name:"); stringName1 =Console.ReadLine (); Console.Write ("Please enter the age of the first student:"); stringAge1 =Console.ReadLine (); Console.Write ("Please enter the first Student's language score:"); stringChinese1 =Console.ReadLine (); Console.Write ("Please enter your first Student's math score:"); stringMath1 =Console.ReadLine (); Console.Write ("Please enter the first Student's English score:"); stringENGLISH1 =Console.ReadLine (); Console.WriteLine ("--------------------------------------------------"); Console.Write ("Please enter a second student's name:"); stringName2 =Console.ReadLine (); Console.Write ("Please enter a second student's age:"); stringAge2 =Console.ReadLine (); Console.Write ("Please enter a second student's language score:"); stringChinese2 =Console.ReadLine (); Console.Write ("Please enter a second student's math score:"); stringMath2 =Console.ReadLine (); Console.Write ("Please enter the second student's English score:"); stringENGLISH2 =Console.ReadLine (); Console.WriteLine ("---------------------------------------------------"); Console.Write ("Please enter a third student's name:"); stringName3 =Console.ReadLine (); Console.Write ("Please enter a third student's age:"); stringAge3 =Console.ReadLine (); Console.Write ("Please enter a third student's language score:"); stringCHINESE3 =Console.ReadLine (); Console.Write ("Please enter a third student's math score:"); stringMath3 =Console.ReadLine (); Console.Write ("Please enter the third student's English score:"); stringENGLISH3 =Console.ReadLine (); Console.WriteLine ("-------------------results show------------------------"); DoubleFirst = convert.todouble (chinese1) +convert.todouble (math1) +convert.todouble (ENGLISH1); Console.WriteLine (name1+"The language score is: ""+chinese1+"", the math score is:""+math1+"", the English score is:""+english1+"", the total score is:""+first+"". "); DoubleSecond=convert.todouble (CHINESE2) +convert.todouble (math2) +convert.todouble (ENGLISH2); Console.WriteLine (name2+"The language score is: ""+chinese2+"", the math score is:""+math2+"", the English score is:""+english2+"", the total score is:""+second+"". "); DoubleThird=convert.todouble (CHINESE3) +convert.todouble (MATH3) +convert.todouble (ENGLISH3); Console.WriteLine (Name3+"The language score is: ""+chinese3+"", the math score is:""+math3+"", the English score is:""+english3+"", the total score is:""+third+"". "); Double Yuwen=convert.todouble (CHINESE1) +convert.todouble (CHINESE2) +convert.todouble (CHINESE3); Doubleyw=convert.todouble (Yuwen); Console.WriteLine ("The language score is ""+ Yuwen +"", the average score is""+yw/3+"". "); DoubleShuxue=convert.todouble (math1) +convert.todouble (math2) +convert.todouble (MATH3); Doublesx=convert.todouble (Shuxue); Console.WriteLine ("The math score is ""+shuxue+"", the average score is""+sx/3+"". "); DoubleYingyu=convert.todouble (ENGLISH1) +convert.todouble (ENGLISH2) +convert.todouble (ENGLISH3); Doubleyy=convert.todouble (Yingyu); Console.WriteLine ("The total English score is ""+yingyu+"", the average score is""+yy/3+"". "); Console.WriteLine ("The sum of all the account scores for all people is ""+ (Yuwen+shuxue+yingyu) +"". "); Console.ReadLine ();

"2017-2-19" C # data type, data conversion, variables, constants, escape characters