C# Demo Application Illustrating the Use of Regular Expressions with The .NET Framework

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using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; // This line allows us to use classes like Regex and Match // without having to spell out the entire location. using System.Text.RegularExpressions; namespace RegexDemo { /// <summary> /// Application showing the use of regular expressions in the .NET framework /// Copyright (c) 2003 Jan Goyvaerts. All rights reserved. /// Visit http://www.regular-expressions.info for a detailed tutorial to regular expressions. /// /// This source code is provided for educational purposes only, without /// any warranty of any kind. Distribution of this source code and/or the /// application compiled from this source code is prohibited. Please refer /// everybody interested in getting a copy of the source code to /// http://www.regular-expressions.info where it can be downloaded. /// </summary> public class FormRegex : System.Windows.Forms.Form { // Designer-generated code to create the form has been omitted for brevity C# Demo Application Illustrating the Use of Regular Expressions with The .NET Framework

C# Demo Application Illustrating the Use of Regular Expressions with The .NET Framework

private void checkDotAll_Click(object sender, System.EventArgs e) { // "Dot all" and "ECMAScript" are mutually exclusive options. if (checkDotAll.Checked) checkECMAScript.Checked = false; } private void checkECMAScript_Click(object sender, System.EventArgs e) { // "Dot all" and "ECMAScript" are mutually exclusive options. if (checkECMAScript.Checked) checkDotAll.Checked = false; } private RegexOptions getRegexOptions() { // "Dot all" and "ECMAScript" are mutually exclusive options. // If we include them both, then the Regex() constructor or the // Regex.Match() method will raise an exception System.Diagnostics.Trace.Assert( !(checkDotAll.Checked && checkECMAScript.Checked), "DotAll and ECMAScript options are mutually exclusive"); // Construct a RegexOptions object // If the options are predetermined, you can simply pass something like // RegexOptions.Multiline | RegexOptions.Ignorecase // directly to the Regex() constructor or the Regex.Match() method RegexOptions options = new RegexOptions(); // If true, the dot matches any character, including a newline // If false, the dot matches any character, except a newline if (checkDotAll.Checked) options |= RegexOptions.Singleline; // If true, the caret ^ matches after a newline, and the dollar $ matches // before a newline, as well as at the start and end of the subject string // If false, the caret only matches at the start of the string // and the dollar only at the end of the string if (checkMultiLine.Checked) options |= RegexOptions.Multiline; // If true, the regex is matched case insensitively if (checkIgnoreCase.Checked) options |= RegexOptions.IgnoreCase; // If true, \w, \d and \s match ASCII characters only, // and \10 is backreference 1 followed by a literal 0 // rather than octal escape 10. if (checkECMAScript.Checked) options |= RegexOptions.ECMAScript; return options; } private void btnMatch_Click(object sender, System.EventArgs e) { // This method illustrates the easiest way to test if a string can be // matched by a regex using the System.Text.RegularExpressions.Regex.Match // static method. This way is recommended when you only want to validate // a single string every now and then. // Note that IsMatch() will also return True if the regex matches part of // the string only. If you only want it to return True if the regex matches // the entire string, simply prepend a caret and append a dollar sign // to the regex to anchor it at the start and end. // Note that when typing in a regular expression into textSubject, // backslashes are interpreted at the regex level. // So typing in \( will match a literal ( character and \\ matches a // literal backslash. When passing literal strings in your source code, // you need to escape backslashes in strings as usual. // So the string "\\(" matches a literal ( and "\\\\" matches a single // literal backslash. // To reduce confusion, I suggest you use verbatim strings instead: // @"\(" matches a literal ( and @"\\" matches a literal backslash. // You can omit the last parameter with the regex options // if you don't want to specify any. textReplaceResults.Text = "N/A"; try { if (Regex.IsMatch(textSubject.Text, textRegex.Text, getRegexOptions())) { textResults.Text = "The regex matches part or all of the subject"; } else { textResults.Text = "The regex cannot be matched in the subject"; } } catch (Exception ex) { // Most likely cause is a syntax error in the regular expression textResults.Text = "Regex.IsMatch() threw an exception:\r\n" + ex.Message; } } private void btnGetMatch_Click(object sender, System.EventArgs e) { // Illustrates the easiest way to get the text of the first match // using the System.Text.RegularExpressions.Regex.Match static method. // Useful for easily extracting a string form another string. // You can omit the last parameter with the regex options // if you don't want to specify any. // If there's no match, Regex.Match.Value returns an empty string. // If you are only interested in part of the regex match, you can use // .Groups[3].Value instead of .Value to get the text matched between // the third pair of round brackets in the regular expression textReplaceResults.Text = "N/A"; try { textResults.Text = Regex.Match(textSubject.Text, textRegex.Text, getRegexOptions()).Value; } catch (Exception ex) { // Most likely cause is a syntax error in the regular expression textResults.Text = "Regex.Match() threw an exception:\r\n" + ex.Message; } } private void btnReplace_Click(object sender, System.EventArgs e) { // Illustrates the easiest way to do a regex-based search-and-replace on // a single string using the System.Text.RegularExpressions.Regex.Replace // static method. This method will replace ALL matches of the regex in // the subject with the replacement text. // If there are no matches, Replace() returns the subject string unchanged. // If you only want to replace certain matches, you have to use the method // illustrated in btnRegexObjReplace_click. // You can omit the last parameter with the regex options // if you don't want to specify any. // In the replacement text (textReplace.Text), you can use $& to insert // the entire regex match, and $1, $2, $3, etc. for the backreferences // (text matched by the part in the regex between the first, second, // third, etc. pair of round brackets) // $$ inserts a single $ character // $` (dollar backtick) inserts the text in the subject / to the left of the regex match // $' (dollar single quote) inserts the text in the subject // to the right of the end of the regex match // $_ inserts the entire subject text try { textReplaceResults.Text = Regex.Replace(textSubject.Text, textRegex.Text, textReplace.Text, getRegexOptions()); textResults.Text = "N/A"; } catch (Exception ex) { // Most likely cause is a syntax error in the regular expression textResults.Text = "Regex.Replace() threw an exception:\r\n" + ex.Message; textReplaceResults.Text = "N/A"; } } private void printSplitArray(string[] array) { textResults.Text = ""; for (int i = 0; i < array.Length; i++) { textResults.AppendText(i.ToString() + ": \"" + array[i] + "\"\r\n"); } } private void btnSplit_Click(object sender, System.EventArgs e) { // Regex.Split allows you to split a single string into an array of strings // using a regular expression. This example illustrates the easiest way // to do this; use btnRegexObjSplit_Click if you need to split many strings. // The string is cut at each point where the regex matches. The part of // the string matched by the regex is thrown away. If the regex contains // capturing parentheses, then the part of the string matched by each of // them is also inserted into the array. // To summarize, the array will contain // (indenting for clarity; the array is one-dimensional): // - the part of the string before the first regex match // - the part of the string captured in the first pair of parentheses // in the first regex match // - the part of the string captured in the second pair of parentheses // in the first regex match // - etc. until the last pair of parentheses in the first match // - the part of the string after the first match, and before the 2nd match // - capturing parentheses for the second match // - etc. for all regex matches // - part of the string after the last regex match // Tips: If you want the delimiters to be separate items in the array, // put round brackets around the entire regex. // If you need parentheses for grouping, but don't want their results // in the array, use (?:subregex) non-capturing parentheses. // If you want the delimiters to be included with the split items // in the array, use lookahead or lookbehind to match a position // in the string rather than characters. // E.g.: The regex "," separates a comma-delimited list, deleting the commas // The regex "(,)" separates a comma-delimited list, inserting the // commas as separate strings into the array of strings. // The regex "(?<=,)" separates a comma-delimited list, leaving the // commas at the end of each string in the array. // You can omit the last parameter with the regex options // if you don't want to specify any. textReplaceResults.Text = "N/A"; try { printSplitArray(Regex.Split(textSubject.Text, textRegex.Text, getRegexOptions())); } catch (Exception ex) { // Most likely cause is a syntax error in the regular expression textResults.Text = "Regex.Split() threw an exception:\r\n" + ex.Message; } } private Regex regexObj; private Match matchObj; private void printMatch() { // Regex.Match constructs and returns a Match object // You can query this object to get all possible information about the match if (matchObj.Success) { textResults.Text = "Match offset: " + matchObj.Index.ToString() + "\r\n"; textResults.Text += "Match length: " + matchObj.Length.ToString() +"\r\n"; textResults.Text += "Matched text: " + matchObj.Value + "\r\n"; if (matchObj.Groups.Count > 1) { // matchObj.Groups[0] holds the entire regex match also held by // matchObj itself. The other Group objects hold the matches for // capturing parentheses in the regex for (int i = 1; i < matchObj.Groups.Count; i++) { Group g = matchObj.Groups[i]; if (g.Success) { textResults.Text += "Group " + i.ToString() + " offset: " + g.Index.ToString() + "\r\n"; textResults.Text += "Group " + i.ToString() + " length: " + g.Length.ToString() + "\r\n"; textResults.Text += "Group " + i.ToString() + " text: " + g.Value + "\r\n"; } else { textResults.Text += "Group " + i.ToString() + " did not participate in the overall match\r\n"; } } } else { textResults.Text += "no backreferences/groups"; } } else { textResults.Text = "no match"; } textReplaceResults.Text = "N/A"; } private void btnRegexObj_Click(object sender, System.EventArgs e) { // Clean up, in case we cannot construct the new regex object regexObj = null; textReplaceResults.Text = "N/A"; // If you want to do many searches using the same regular expression, // you should first construct a System.Text.RegularExpressions.Regex object // and then call its Match method (one of the overloaded forms that does // not take the regular expression as a parameter) // regexOptions may be omitted if all options are off try { regexObj = new Regex(textRegex.Text, getRegexOptions()); textResults.Text = "Regex object constructed. Click on one of the " + "buttons to the right of the Create Object button to use the object."; } catch (Exception ex) { // Most likely cause is a syntax error in the regular expression textResults.Text = "Regex constructor threw an exception:\r\n" + ex.Message; return; } } private void btnFirstMatch_Click(object sender, System.EventArgs e) { // Find the first match using regexObj constructed in btnRegexObj_Click() // and store all the details in matchObj // matchObj is used in btnNextMatch_click() to find subsequent matches if (regexObj == null) { textResults.Text = "First click on Create Object to create the regular " + "expression object. Then click on First Match to find " + "the first match in the subject string."; textReplaceResults.Text = "N/A"; } else { matchObj = regexObj.Match(textSubject.Text); printMatch(); } } private void btnNextMatch_Click(object sender, System.EventArgs e) { // Tell the regex engine to find another match after the previous match // Note that even if you change textRegex.Text or textSubject.Text between // clicking btnRegexObj, btnFirstMatch and btnNextMatch, the regex engine // will continue to search the same subject string passed in the // regexObj.Match call in btnFirstMatch_Click using the same regular // expression passed to the Regex() constructor in btnRegexObj_Click if (matchObj == null) { textResults.Text = "Use the First Match button to find the 1st match." + "Then use this button to find following matches."; textReplaceResults.Text = "N/A"; } else { matchObj = matchObj.NextMatch(); printMatch(); } } private void btnRegexObjReplace_Click(object sender, System.EventArgs e) { // If you want to do many search-and-replace operations using the same // regular expression, you should first construct a // System.Text.RegularExpressions.Regex object and then call its Replace() // method (one of the overloaded forms that does not take the regular // expression as a parameter). // This way also allows to to specify two additional parameters allowing // you to control how many replacements will be made. // The easy way used in btnReplace_click will always replace ALL matches. // See the comments with btnReplace_click for explanation of the special // $-placeholders you can use in the replacement text. // You can mix calls to regexObj.Match() and regexObj.Replace() as you like. // The results of the calls will not affect the other calls. if (regexObj == null) { textReplaceResults.Text = "Please use the Create Objects button to" + "construct the regex object.\r\n" + "Then use this button to do a search-and-replace using the subject" + "and replacement texts."; } else { // As used in this example, Replace() will replace ALL matches of the // regex in the subject with the replacement text. // If you want to limit the number of matches replaced, specify a third // parameter with the number of matches to be replaced. // If you specify 3, the first (left-to-right) 3 matches will be replaced. // You can also specify a fourth parameter with the character position // in the subject where the regex search should begin. // If the third parameter is negative, all matches after the starting // position will be replaced like when the third and fourth parameters // are omitted. textReplaceResults.Text = regexObj.Replace(textSubject.Text, textReplace.Text /*, ReplaceCount, ReplaceStart*/ ); } textResults.Text = "N/A"; } private void btnRegexObjSplit_Click(object sender, System.EventArgs e) { // If you want to split many strings using the same regular expression, // you should first construct a System.Text.RegularExpressions.Regex object // and then call its Split method (one of the overloaded forms that does // not take the regular expression as a parameter). // See btnSplit_Click for an explanation how Split() works. // If you first construct a Regex object, you can specify two additional // parameters to Split() after the subject string. // The optional second parameter indicates how many times Split() is // allowed to split the string. A negative number causes the string to be // split at all regex matches. If the number is smaller than the number // of possible matches, then the last string in the returned array // will contain the unsplit remainder of the string. // The optional third parameter indicates the character position in the // string where Split() can start to look for regex matches. // If you specify the third parameter, then the first string in the returned // array will contain the unsplit start of the string as well as // the part of the string between the starting position and the first match. // You can mix calls to regexObj.Match() and regexObj.Split() as you like. // The results of the calls will not affect the other calls. textReplaceResults.Text = "N/A"; if (regexObj == null) { textResults.Text = "Please use the Create Objects button to construct" + "the regular expression object.\r\n" + "Then use this button to split the subject into an array of strings."; } else { printSplitArray(regexObj.Split(textSubject.Text) /*, SplitCount, SplitStart*/ ); } } } }

Get RegexBuddy and easily use the power of regular expressions in C# and VB.NET.