C # <basics> Study Notes (3) - [operator]

(A) Type Conversion Convert

• Compatible type two variables, automatic type conversions may be used, or cast;
• When two variable types are not compatible when using the Convert
• In fact Convert the ground floor, in converted to int when it is int.Parse (need to convert content) calls; so a direct call int.Parse () more efficient
• Each type has a type .Parse ()

//int.TryParse()
bool b = int.TryParse("123", out number);
//这个句子，尝试将一个字符串转换为int，转换成功，则赋值给number，返回true；转换失败，number赋值为0，返回false；
//并不会抛出异常

//使用Convert，下面有很多转换类型
double d = Convert.ToDouble("123.456789");
Console.WriteLine("这个数字是{0:0.00}", d);
//输出123.46（数字Double类型）;在占位符中使用冒号

*** NOTE: *** use the Convert time, can be converted to common sense, such as "123ABC", can not be converted to int32;

(Ii) simple calculations

int i = 10；
Console.WriteLine(i++);//输出10

int i = 10；
Console.WriteLine(++i);//输出11
//符号i--与--i类似

*** NOTE: *** unary operator has higher precedence than a binary operator; unary operators that only operand;

(Iii) relational operators, and logical operators

• Relational operators>, <,> =, <=, ==,! =;
• bool type described right or wrong, only two values ​​true, false

The results relational expression is of type bool;

• &&, ||,! Three logical expression

The value of the logical operator expression or relationship on both sides are generally of the type bool ; higher priority than logical AND or logical, but are preferably small brackets;

(D) if, if-else branch structure

• Sequence Structure
• Branch structure: if, if-else
• Selection structure: if-else-if, switch-case
• Loop structure: while, do-while, for, foreach

//语法
if(判断条件)
{
	要执行的代码;//条件成立时
}
else
{
	要执行的代码；//条件不成立时
}
//先判断再执行；这是一个分支结构，判断所执行的分支；

//处理多条件区间性的判断
if(判断条件)
{
	执行语句;//条件成立
}
else if(条件判断)
{
	执行语句;//条件成立
}
else if(条件判断)
{
	执行语句;//条件成立
}
else if(条件判断)
{
	执行语句;//条件成立
}