C # common classes and Methods

1. datetime numeric type
System. datetime currenttime = new system. datetime ();
1.1 take the current year, month, day, hour, minute, second
Currenttime = system. datetime. now;
1.2 get current year
Int year = currenttime. Year;
1.3 take the current month
Int month = currenttime. month;
1.4 get the current day
Int day = currenttime. Day;
1.5 current time
Int = currenttime. hour;
1.6 get the current score
Int = currenttime. minute;
1.7 takes the current second
Int second = currenttime. Second;
1.8 takes the current millisecond
Int millisecond = currenttime. millisecond;
(The variable can be in Chinese)
1.9 display Chinese date -- year, month, and day
String stry = currenttime. tostring ("F"); // seconds not displayed
1.10 use Chinese date to display _ year and month
String strym = currenttime. tostring ("Y ");
1.11 retrieve Chinese Date display _ month/day
String strmd = currenttime. tostring ("M ");
1.12 take the current year, month, and day in the format of 2003-9-23
String strymd = currenttime. tostring ("D ");
1.13 get the current time, format: 14: 24
String strt = currenttime. tostring ("T ");

2. Convert string type to 32-digit font
Int32.parse (variable) int32.parse ("constant ")
3. Variable. tostring ()
Convert string to string
12345. tostring ("N"); // generate 12,345.00
12345. tostring ("C"); // generate $12,345.00
12345. tostring ("e"); // generate 1.234500e + 004
12345. tostring ("F4"); // generate 12345.0000
12345. tostring ("X"); // generate 3039 (hexadecimal)
12345. tostring ("p"); // generate 1,234,500.00%

4. Variable. Length numeric type
String Length:
For example, string STR = "China ";
Int Len = Str. length; // Len is a custom variable, and STR is the variable name of the string to be tested.

5. Convert the character code into a bit code
System. Text. encoding. Default. getbytes (variable)
For example, byte [] bytstr = system. Text. encoding. Default. getbytes (STR );
Then we can get the bit length:
Len = bytstr. length;

6. system. Text. stringbuilder ("")
String addition, (is the same as the + number ?)
For example:
System. Text. stringbuilder sb = new system. Text. stringbuilder ("");
SB. append ("China ");
SB. append ("people ");
SB. append ("Republic ");

7. Variable. substring (parameter 1, parameter 2 );
Part of the string to be truncated. Parameter 1 is the start number of digits on the left, and parameter 2 is the number of digits to be truncated.
For example, string S1 = Str. substring );

8. Obtain the IP address of a remote user.
String user_ip = request. servervariables ["remote_addr"]. tostring ();

9. Obtain the real IP address of the remote user through the proxy server:
If (request. servervariables ["http_via"]! = NULL ){
String user_ip = request. servervariables ["http_x_forwarded_for"]. tostring ();
} Else {
String user_ip = request. servervariables ["remote_addr"]. tostring ();
}

10. Access session Value
Session ["variable"];
For example, assign a value:
Session ["username"] = "Bush ";
Valid value:
Object objname = session ["username"];
String strname = objname. tostring ();
Clear:
Session. removeall ();

11. Send variables with hyperlinks
String STR = request. querystring ["variable"];
For example, create a hyperlink on any page: <a href = edit. aspx? Fbid = 23> click </a>
On the edit. ASPX page, set the value to string STR = request. querystring ["fdid"];

12. Create a new node for the XML document
Doc object. createelement ("new node name ");

13. Add the new child node to the parent node of the XML document.
Parent node. appendchild (child node );

14. delete a node
Parent node. removechild (node );

15. output to the page: Response
Response. Write ("string ");
Response. Write (variable );
Jump to the page specified by the URL:
Response. Redirect ("url address ");

16. Check whether the specified position contains null characters.
Char. iswhitespce (STRING variable, number of digits) -- Logical type;
For example:
String STR = "Chinese people ";
Response. Write (char. iswhitespace (STR, 2); // The result is true. The first character is 0, and the second is the third character.

17. Check whether the character is a punctuation mark.
Char. ispunctuation (''character'') -- Logical type
For example:
Response. Write (char. ispunctuation (''a'); // return value: false

18. Convert the character into a number and check the code. Note that it is a single quotation mark.
(INT) '''character''
For example:
Response. Write (INT) ''in''); // The code with the result being a Chinese character: 20013

19. Convert the number into characters and check the characters represented by the Code: (char) Code
For example:
Response. Write (char) 22269); // return the word "country.

20. Clear spaces before and after the string: trim ()
21. String replacement
String variable. Replace ("substring", "Replace ")
For example:
String STR = "China ";
STR = Str. Replace ("country", "Central"); // Replace the Chinese character with the central character
Response. Write (STR); // The output result is "Central"
Another example is: (this is very practical)
String STR = "This Is A <SCRIPT> script ";
STR = Str. replace ("<", "<font> </font> "); // Replace the left angle brackets with <font> and </font> (or replace them with <, but it is estimated that after saving the XML, it will be restored again)
Response. Write (STR); // display as: "This is a <SCRIPT> script"
If not replaced, <SCRIPT> is not displayed. If it is a script, it runs. If it is replaced, the script does not run.
The value of this Code is that you can invalidate and display all HTML tags in a text file to protect your interactive websites.
Specific implementation: Add the following code to your form submission button script:
String strsubmit = label1.text; // label1 is the Control ID for you to submit data.
Strsubmit = strsubmit. Replace ("<", "<font> </font> ");
Then save or output strsubmit.
This method can also be used to easily implement the UBB code.

22. Maximum values in I and j: Math. Max (I, j)
For example, int x = math. Max (5, 10); // X, the value is 10.
Add a bit. 23. String comparison ......

23. String comparison is generally used: If (str1 = str2) {}, but there are other methods:
(1 ),
String str1; str2
// Syntax: str1.endswith (str2); _ check whether str1 ends with str2 and returns a Boolean value. For example:
If (str1.endswith (str2) {response. Write ("string str1 ends with" + str2 + ");}
　　

(2 ),
// Syntax: str1.equals (str2); _ check whether str1 is equal to str2. Return a Boolean value, which is the same as the preceding syntax.
　　

(3 ),
// Syntax equals (str1, str2); _ checks whether str1 is equal to str2 and returns a Boolean value.

24. Find the position where the specified character or string appears for the first time (the last time) in the string, and return the index values: indexof () and lastindexof (), for example:
Str1.indexof ("word"); // search for the index value (location) of the word in str1)
Str1.indexof ("string"); // search for the index value (location) of the first character of "string" in str1)
Str1.indexof ("string", 4th); // query the index value (location) of the first character of the "string" in str1 for 2 characters starting from str1 characters)

25. Specify the index bit in the string to insert the specified character: insert (), for example:
Str1.insert (1, "word"); Insert "word" to the second character of str1. If str1 = "China", it is inserted as "Chinese country ";

26. Add spaces or specified char characters to the left (or right) of the string so that the string reaches the specified length: padleft () and padright (), for example:
<%
String str1 = "Chinese ";
Str1 = str1.padleft (10, ''1''); // if no second parameter is specified, a space is added.
Response. Write (str1); // The result is "1111111 Chinese" and the string length is 10.
%>

27. Delete the specified number of characters from the specified position: Remove ()

28. Reverse the order of elements in the entire one-dimensional array.
Har [] chararray = "ABCDE". tochararray ();
Array. Reverse (chararray );
Console. writeline (new string (chararray ));

29. Determine whether the nth character in a string is capitalized.
String STR = "abceedddd ";
Response. Write (char. isupper (STR, 3 ));

Source: http://www.chinacs.net/archives/1/2006/3515.html