Adhere to ASP.NET - (5)

xiaoxiao2021-03-06  85

Data character type in C #:

String cannot be stored in the stack, obviously belongs to the reference type; CHAR is clearly worthy of value type.

String Type:

Declare a string type, not create a string object in the stack, but only a string reference is created in the stack, and there is no reference object.

A string that does not contain any character, called an empty string.

CHAR (Character) Type:

Store the text in the form of several characters in the CHAR variable, and it is stored as a 16-bit value form between 0 to 65535, represents a Unicode character.

Side character:

/' apostrophe

/" Double quotes

// slash

/ 0 null value

/ a alarm

/ B back

/ f change page

/ N wrap

/ r Enter

/ T Table Character

/ v vertical list

Tip: If the prefix of the string is @, then the subsequent string will be explained in accordance with its actual display, there is no exemplary character.

Another purpose of the escape character: CHAR C = "/ vuxxx", can give C assigning a keyboard or not a regular character.

Boolean type:

Only two values: True or False

The C # is not allowed to represent the variable of the Boolean type to any value that is not TRUE or FALSE.

Object type:

In C #, the Object type is a common type, which can represent any data type, so the type of base type, the system.object, which only determines its value in operation, and another representation is: Object.

Processing date data:

DateTime Date;

But can't assign this: Date = "10/02/1998";

It should be: date = convert.todatetime ("10/02/1998");

The value is not stored in the form of characters, but it cannot be assigned a value to be assigned, only a value of the date format can be assigned.

If you want to display on the web page, you must convert the date to a string form: strIMG DateTime = Date.toString ();

Fourth, operator

1, assignment operation:

2, arithmetic operation:

/ Division

% Try / Remain

3, the priority of the operator:

Weaken from top to bottom:

, -, one yuan -

*, /,%

,

=, =, - , * =

V. Connect strings:

And = application.

Sixth, the conversion between data types

1, implicit conversion

2, display conversion (forced conversion)

INT NUM1 = 66;

INT NUM2 = 35;

Double xxx;

XXX = NUM1 / NUM2; // There is data loss;

XXX = (double) NUM1 / NUM2; / / correct execution, equivalent to xxx = (double) NUM1 / (Double) Num2;

The priority of the mandatory type conversion is second only to the priority of parentheses, so the previous execution is not the same as XXX = (Num1 / Num2);

You cannot convert between the values ​​and BOOL.

3, invalid mandatory type conversion

In order to avoid this, we use this technology:

Long Intnumber = 250000000;

INT xxxx;

Checked

{

XXXX = (int) intNumber;

}

4, data conversion

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