Example 365 (10) --------- common character verification techniques for Regular Expressions

I. use regular expressions to check repeated words in a string,

Ii. Code

Using System; using System. collections. generic; using System. componentModel; using System. data; using System. drawing; using System. text; using System. windows. forms; namespace ValidateWord {public partial class Frm_Main: Form {public Frm_Main () {InitializeComponent ();} private void button#click (object sender, EventArgs e) {/* \ escape character, escape a character with special functions into a common character, or in turn match the start position of the input string $ match the end position of the input string * match the previous zero or multiple When the sub-expression + matches the previous one or more sub-expressions? Match the previous zero or one subexpression {n} n is a non-negative integer. Match the previous n subexpressions {n,} n is a non-negative integer, at least match the previous n subexpressions {n, m} m and n are non-negative integers, where n <= m, at least n times and at most m times? When this character is followed by other delimiters (*, + ,?, If {n}, {n ,}, {n, m}) is followed, the matching mode matches as few strings as possible. match any single character except "\ n" (pattern) to match pattern and obtain this match (?: Pattern) matches pattern but does not get the matching result (? = Pattern) Forward pre-query. Match the search string (?! Pattern) negative pre-query. If the string does not match pattern, match the search string x | y to match x or y. For example, 'z | food' can match "z" or "food ". '(Z | f) ood' matches "zood" or "food" [xyz] character set. Match any character in it. For example, '[abc]' can match 'A' [^ xyz] negative value character set in 'plain. Match any character not included. For example, '[^ abc]' can match 'P' [a-z] In 'plain 'to match any character in the specified range. For example, '[a-z]' can match any lowercase letter character [^ a-z] within the range of 'A' to 'Z. For example, '[^ a-z]' can match a value other than 'A '~ Any character \ B in 'z'' matches a word boundary. It indicates the position between the word and the space \ B matches non-word boundary \ d matches a digit character, it is equivalent to [0-9] \ D matching a non-numeric character, it is equivalent to [^ 0-9] \ f matching a linefeed \ n matching a linefeed \ r matching a carriage return \ s matching any blank characters, including spaces, tabs, and page breaks. \ S matches any non-blank characters. \ t matches a tab. \ v matches a vertical tab. It is equivalent to matching any word characters including underlines with \ x0b and \ cK \ w. It is equivalent to ''[A-Za-z0-9 _] '\ W matching any non-word character. It is equivalent to '[^ A-Za-z0-9 _]' \ k <name> named back reference. For example ,(? <Char> \ w) \ k <char> searches for double-write word characters. Expression (? <43> \ w) \ 43. You can use single quotes to replace angle brackets, for example, \ k'char '. (? <Name> subexpression) captures the matched subexpression to a group name or number name. The string used for name cannot contain any punctuation marks and cannot start with a number. You can use single quotes to replace angle brackets, such (? 'Name '). */System. Text. RegularExpressions. MatchCollection matches = // use a regular expression to search for the System. Text. RegularExpressions. Regex. Matches (label1.Text, @ "\ B (? <Word> \ w +) \ s + (\ k <word>) \ B ", System. text. regularExpressions. regexOptions. compiled | System. text. regularExpressions. regexOptions. ignoreCase); if (matches. count! = 0) // If the set contains content {foreach (System. text. regularExpressions. match // traverse the set match in matches) {string word = match. groups ["word"]. value; // obtain the duplicate message box. show (word. toString (), "English word"); // The message dialog box is displayed.} else {MessageBox. show ("No duplicate words");} // pop-up message dialog box} private void Form1_Load (object sender, EventArgs e) {label1.Text = // create a String object "The quick brown fox jumped over the lazy dog. ";}}}

3. Use a regular expression to replace a string,

4. Code

Using System; using System. collections. generic; using System. componentModel; using System. data; using System. drawing; using System. text; using System. windows. forms; namespace ReplaceStr {public partial class Frm_Main: Form {public Frm_Main () {InitializeComponent ();} private void button#click (object sender, EventArgs e) {/* input type: System. string: the String to be matched. Pattern type: the regular expression pattern to be matched by System. String. Replacement type: System. String replacement String. */String strResult = System. Text. RegularExpressions. Regex. // Replace the string Replace (textBox1.Text, @ "[A-Za-z] \ *? ", TextBox2.Text); MessageBox. show ("replace Prefix:" + "\ n" + textBox1.Text + // the character to be replaced by "\ n" + "in the pop-up message dialog box: "+" \ n "+ textBox2.Text +" \ n "+" character after replacement: "+" \ n "+ strResult," replace ");} private void button2_Click (object sender, EventArgs e) {Close (); // Close the form }}}

5. Use regular expressions to split strings,

Vi. Code

Using System; using System. collections. generic; using System. componentModel; using System. data; using System. drawing; using System. text; using System. windows. forms; namespace ValidateSplit {public partial class Frm_Main: Form {public Frm_Main () {InitializeComponent ();} private void btn_Split_Click (object sender, EventArgs e) {string [] P_Str = System. text. regularExpressions. // use a regular expression to split the Regex according to the number. split (txt_Split.Text, "[1-9]"); foreach (string s in P_Str) // traverses the Split string set {txt_Result.Text + = s; // display string} private void btn_Close_Click (object sender, EventArgs e) {Application. exit (); // Exit the application }}}

7. Use regular expressions to verify the input letters,

8: Code

Using System; using System. collections. generic; using System. componentModel; using System. data; using System. drawing; using System. text; using System. windows. forms; namespace IsLetter {public partial class Frm_Main: Form {public Frm_Main () {InitializeComponent ();} private void btn_Validate_Click (object sender, EventArgs e) {if (! IsLetter (textBox1.Text. Trim () // check whether the string is composed of uppercase and lowercase letters {MessageBox. Show ("the input is not a letter !!! "," Prompt ") ;}// the pop-up message dialog box else {MessageBox. Show (" the input is a letter !!!!! "," Prompt ");} // pop-up message dialog box} // <summary> // verify whether the string is composed of uppercase and lowercase letters /// </summary> /// <param name = "str_Letter"> string </param> // <returns> returns a Boolean value </returns> public bool IsLetter (string str_Letter) {return System. text. regularExpressions. regex. // use A regular expression to determine if IsMatch (str_Letter, @ "^ [A-Za-z] + $ ");}}}

9. Verification of other common characters

Use regular expressions to verify Chinese Character Input @ "^ [\ u4e00-\ u9fa5], {0,} $"

Use a regular expression to verify whether the length of the input string is greater than 8 @ "^. {8,} $"

Use regular expressions to verify the E-mail format @ "^ ([\ w-\.] +) @ (\ [0-9] {1, 3 }\. [0-9] {1, 3 }\. [0-9] {1, 3 }\.) | ([\ w-] + \.) +) ([a-zA-Z] {2, 4} | [0-9] {1, 3}) (\]?) $ ")

Use a regular expression to verify the IP address "(25 [0-5] | 2 [0-4] \ d | [0-1] \ d {2} | [1-9 ]? \ D )"

Use a regular expression to verify URL @ "http (s )? : // ([\ W-] + \.) + [\ w-] + (/[\ w -./? % & =] *)? "