I am providing a textbox for one to enter a Regular Expression to match filenames. I plan to detect any named capture groups that they provide with the Regex method GetGroupNames().
I want to get the expression that they entered inside each named capture group.
As an example, they might enter a regular expression like this:
December (?<FileYear>\d{4}) Records\.xlsx
Is there a method or means to get the sub-expression \d{4} apart from manually parsing the regular expression string?
Here is an ugly brute force extension for parsing without using another Regex to detect the subexpression (or subpattern):
public static string GetSubExpression(this Regex pRegex, string pCaptureName)
{
string sRegex = pRegex.ToString();
string sGroupText = #"(?<" + pCaptureName + ">";
int iStartSearchAt = sRegex.IndexOf(sGroupText) + sGroupText.Length;
string sRemainder = sRegex.Substring(iStartSearchAt);
string sThis;
string sPrev = "";
int iOpenParenCount = 0;
int iEnd = 0;
for (int i = 0; i < sRemainder.Length; i++)
{
sThis = sRemainder.Substring(i, 1);
if (sThis == ")" && sPrev != #"\" && iOpenParenCount == 0)
{
iEnd = i;
break;
}
else if (sThis == ")" && sPrev != #"\")
{
iOpenParenCount--;
}
else if (sThis == "(" && sPrev != #"\")
{
iOpenParenCount++;
}
sPrev = sThis;
}
return sRemainder.Substring(0, iEnd);
}
The usage looks like this:
Regex reFromUser = new Regex(txtFromUser.Text);
string[] asGroupNames = reFromUser.GetGroupNames();
int iItsInt;
foreach (string sGroupName in asGroupNames)
{
if (!Int32.TryParse(sGroupName, out iItsInt)) //don't want numbered groups
{
string sSubExpression = reParts.GetSubExpression(sGroupName);
//Do what I need to do with the sub-expression
}
}
Now, if you would like to generate test or sample data, you can use the NuGet package called "Fare" in the following way after you get a sub-expression:
//Generate test data for it
Fare.Xeger X = new Fare.Xeger(sSubExpression);
string sSample = X.Generate();
This pattern (?<=\(\?<\w+\>)([^)]+) will give you all the named match capture expression with the name of the capture. It uses a negative look behind to make sure the text matched will have a (?<...> before it.
string data = #"December (?<FileYear>\d{4}) Records\.xlsx";
string pattern = #"(?<=\(\?<\w+\>)([^)]+)";
Regex.Matches(data, pattern)
.OfType<Match>()
.Select(mt => mt.Groups[0].Value)
returns one item of
\d{4}
While the data such as (?<FileMonth>[^\s]+)\s+(?<FileYear>\d{4}) Records\.xlsx would return two matches:
[^\s]+
\d{4}
Here is a solution using a regular expression to match the capturing groups in a regular expression. Idea is from this post Using RegEx to balance match parenthesis:
\(\?\<(?<MyGroupName>\w+)\>
(?<MyExpression>
((?<BR>\()|(?<-BR>\))|[^()]*)+
)
\)
or more concisely...
\(\?\<(?<MyGroupName>\w+)\>(?<MyExpression>((?<BR>\()|(?<-BR>\))|[^()]*)+)\)
and to use it might look like this:
string sGetCaptures = #"\(\?\<(?<MyGroupName>\w+)\>(?<MyExpression>((?<BR>\()|(?<-BR>\))|[^()]*)+)\)";
MatchCollection MC = Regex.Matches(txtFromUser.Text, sGetCaptures );
foreach (Match M in MC)
{
string sGroupName = M.Groups["MyGroupName"].Value;
string sSubExpression = M.Groups["MyExpression"].Value;
//Do what I need to do with the sub-expression
MessageBox.Show(sGroupName + ":" + sSubExpression);
}
And for the example in the original question, the message box would return FileYear:\d{4}
I have a text say:
Hello
abc
Hello
def
Hello
I want to convert it to
Hello1
abc
Hello2
abc
Hello3
i.e I need to append a number after each occurrence of "Hello" text.
Currently I have written this code:
var xx = File.ReadAllText("D:\\test.txt");
var regex = new Regex("Hello", RegexOptions.IgnoreCase);
var matches = regex.Matches(xx);
int i = 1;
foreach (var match in matches.Cast<Match>())
{
string yy = match.Value;
xx = Replace(xx, match.Index, match.Length, match.Value + (i++));
}
and the Replace method above used is:
public static string Replace(string s, int index, int length, string replacement)
{
var builder = new StringBuilder();
builder.Append(s.Substring(0, index));
builder.Append(replacement);
builder.Append(s.Substring(index + length));
return builder.ToString();
}
Currently the above code is not working and is replacing the text in between.
Can you help me fixing that?
Assuming Hello is just a placeholder for a more complex pattern, here is a simple fix: use a match evaluator inside Regex.Replace where you may use variables:
var s = "Hello\nabc\nHello\ndef\nHello";
var i = 0;
var result = Regex.Replace(
s, "Hello", m => string.Format("{0}{1}",m.Value,++i), RegexOptions.IgnoreCase);
Console.WriteLine(result);
See the C# demo
I've found a lot of examples of how to check something using regex, or how to split text using regular expressions.
But how can I extract words out of a string ?
Example:
aaaa 12312 <asdad> 12334 </asdad>
Lets say I have something like this, and I want to extract all the numbers [0-9]* and put them in a list.
Or if I have 2 different kind of elements:
aaaa 1234 ...... 1234 ::::: asgsgd
And I want to choose digits that come after ..... and words that come after ::::::
Can I extract these strings in a single regex ?
Here's a solution for your first problem:
class Program
{
static void Main(string[] args)
{
string data = "aaaa 12312 <asdad> 12334 </asdad>";
Regex reg = new Regex("[0-9]+");
foreach (var match in reg.Matches(data))
{
Console.WriteLine(match);
}
Console.ReadLine();
}
}
In the general case, you can do this using capturing parentheses:
string input = "aaaa 1234 ...... 1234 ::::: asgsgd";
string regex = #"\.\.\.\. (\d+) ::::: (\w+)";
Match m = Regex.Match(input, regex);
if (m.Success) {
int numberAfterDots = int.Parse(m.Groups[1].Value);
string wordAfterColons = m.Groups[2].Value;
// ... Do something with these values
}
But the first part you asked (extract all the numbers) is a bit easier:
string input = "aaaa 1234 ...... 1234 ::::: asgsgd";
var numbers = Regex.Matches(input, #"\d+")
.Cast<Match>()
.Select(m => int.Parse(m.Value))
.ToList();
Now numbers will be a list of integers.
For your specific examples:
string firstString = "aaaa 12312 <asdad> 12334 </asdad>";
Regex firstRegex = new Regex(#"(?<Digits>[\d]+)", RegexOptions.ExplicitCapture);
if (firstRegex.IsMatch(firstString))
{
MatchCollection firstMatches = firstRegex.Matches(firstString);
foreach (Match match in firstMatches)
{
Console.WriteLine("Digits: " + match.Groups["Digits"].Value);
}
}
string secondString = "aaaa 1234 ...... 1234 ::::: asgsgd";
Regex secondRegex = new Regex(#"([\.]+\s(?<Digits>[\d]+))|([\:]+\s(?<Words>[a-zA-Z]+))", RegexOptions.ExplicitCapture);
if (secondRegex.IsMatch(secondString))
{
MatchCollection secondMatches = secondRegex.Matches(secondString);
foreach (Match match in secondMatches)
{
if (match.Groups["Digits"].Success)
{
Console.WriteLine("Digits: " + match.Groups["Digits"].Value);
}
if (match.Groups["Words"].Success)
{
Console.WriteLine("Words: " + match.Groups["Words"].Value);
}
}
}
Hope that helps. The output is:
Digits: 12312
Digits: 12334
Digits: 1234
Words: asgsgd
Something like this will do nicely!
var text = "aaaa 12312 <asdad> 12334 </asdad>";
var matches = Regex.Matches(text, #"\w+");
var arrayOfMatched = matches.Cast<Match>().Select(m => m.Value).ToArray();
Console.WriteLine(string.Join(", ", arrayOfMatched));
\w+ Matches consecutive word characters. Then we just selected the values out of the list of matches and turn them into an array.
Regex itemsRegex = new Regex(#"(\d*)");
MatchCollection matches = itemsRegex.Matches(text);
int[] values = matches.Cast<Match>().Select(m => Convert.ToInt32(m.Value)).ToArray();
Regex phoneregex = new Regex("[0-9][0-9][0-9]\-[0-9][0-9][0-9][0-9]");
String unicornCanneryDirectory = "unicorn cannery 483-8627 cha..."
String numbersToCall = "";
//the second argument is where to begin within the match,
//we probably want 0, the first character
Match matchIterator = phoneregex.Match(unicornCanneryDirectory , 0);
//Success tells us if matchIterator has another match or not
while( matchIterator.Sucess){
String aResult = matchIterator.Result();
//we could manipulate our match now but I'm going to concatenate them all for later
numbersToCall += aResult + " ";
matchIterator = matchIterator.NextMatch();
}
// use my concatenated matches now
String message = "Unicorn rights activists demand more sparkles in the unicorn canneries under the new law...";
phoneDialer.MassCallWithAutomatedMessage(aResult, message );
http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.match.nextmatch.aspx
Do any of you know of an easy/clean way to find a substring within a string while ignoring some specified characters to find it. I think an example would explain things better:
string: "Hello, -this- is a string"
substring to find: "Hello this"
chars to ignore: "," and "-"
found the substring, result: "Hello, -this"
Using Regex is not a requirement for me, but I added the tag because it feels related.
Update:
To make the requirement clearer: I need the resulting substring with the ignored chars, not just an indication that the given substring exists.
Update 2:
Some of you are reading too much into the example, sorry, i'll give another scenario that should work:
string: "?A&3/3/C)412&"
substring to find: "A41"
chars to ignore: "&", "/", "3", "C", ")"
found the substring, result: "A&3/3/C)41"
And as a bonus (not required per se), it will be great if it's also not safe to assume that the substring to find will not have the ignored chars on it, e.g.: given the last example we should be able to do:
substring to find: "A3C412&"
chars to ignore: "&", "/", "3", "C", ")"
found the substring, result: "A&3/3/C)412&"
Sorry if I wasn't clear before, or still I'm not :).
Update 3:
Thanks to everyone who helped!, this is the implementation I'm working with for now:
http://www.pastebin.com/pYHbb43Z
An here are some tests:
http://www.pastebin.com/qh01GSx2
I'm using some custom extension methods I'm not including but I believe they should be self-explainatory (I will add them if you like)
I've taken a lot of your ideas for the implementation and the tests but I'm giving the answer to #PierrOz because he was one of the firsts, and pointed me in the right direction.
Feel free to keep giving suggestions as alternative solutions or comments on the current state of the impl. if you like.
in your example you would do:
string input = "Hello, -this-, is a string";
string ignore = "[-,]*";
Regex r = new Regex(string.Format("H{0}e{0}l{0}l{0}o{0} {0}t{0}h{0}i{0}s{0}", ignore));
Match m = r.Match(input);
return m.Success ? m.Value : string.Empty;
Dynamically you would build the part [-, ] with all the characters to ignore and you would insert this part between all the characters of your query.
Take care of '-' in the class []: put it at the beginning or at the end
So more generically, it would give something like:
public string Test(string query, string input, char[] ignorelist)
{
string ignorePattern = "[";
for (int i=0; i<ignoreList.Length; i++)
{
if (ignoreList[i] == '-')
{
ignorePattern.Insert(1, "-");
}
else
{
ignorePattern += ignoreList[i];
}
}
ignorePattern += "]*";
for (int i = 0; i < query.Length; i++)
{
pattern += query[0] + ignorepattern;
}
Regex r = new Regex(pattern);
Match m = r.Match(input);
return m.IsSuccess ? m.Value : string.Empty;
}
Here's a non-regex string extension option:
public static class StringExtensions
{
public static bool SubstringSearch(this string s, string value, char[] ignoreChars, out string result)
{
if (String.IsNullOrEmpty(value))
throw new ArgumentException("Search value cannot be null or empty.", "value");
bool found = false;
int matches = 0;
int startIndex = -1;
int length = 0;
for (int i = 0; i < s.Length && !found; i++)
{
if (startIndex == -1)
{
if (s[i] == value[0])
{
startIndex = i;
++matches;
++length;
}
}
else
{
if (s[i] == value[matches])
{
++matches;
++length;
}
else if (ignoreChars != null && ignoreChars.Contains(s[i]))
{
++length;
}
else
{
startIndex = -1;
matches = 0;
length = 0;
}
}
found = (matches == value.Length);
}
if (found)
{
result = s.Substring(startIndex, length);
}
else
{
result = null;
}
return found;
}
}
EDIT: here's an updated solution addressing the points in your recent update. The idea is the same except if you have one substring it will need to insert the ignore pattern between each character. If the substring contains spaces it will split on the spaces and insert the ignore pattern between those words. If you don't have a need for the latter functionality (which was more in line with your original question) then you can remove the Split and if checking that provides that pattern.
Note that this approach is not going to be the most efficient.
string input = #"foo ?A&3/3/C)412& bar A341C2";
string substring = "A41";
string[] ignoredChars = { "&", "/", "3", "C", ")" };
// builds up the ignored pattern and ensures a dash char is placed at the end to avoid unintended ranges
string ignoredPattern = String.Concat("[",
String.Join("", ignoredChars.Where(c => c != "-")
.Select(c => Regex.Escape(c)).ToArray()),
(ignoredChars.Contains("-") ? "-" : ""),
"]*?");
string[] substrings = substring.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
string pattern = "";
if (substrings.Length > 1)
{
pattern = String.Join(ignoredPattern, substrings);
}
else
{
pattern = String.Join(ignoredPattern, substring.Select(c => c.ToString()).ToArray());
}
foreach (Match match in Regex.Matches(input, pattern))
{
Console.WriteLine("Index: {0} -- Match: {1}", match.Index, match.Value);
}
Try this solution out:
string input = "Hello, -this- is a string";
string[] searchStrings = { "Hello", "this" };
string pattern = String.Join(#"\W+", searchStrings);
foreach (Match match in Regex.Matches(input, pattern))
{
Console.WriteLine(match.Value);
}
The \W+ will match any non-alphanumeric character. If you feel like specifying them yourself, you can replace it with a character class of the characters to ignore, such as [ ,.-]+ (always place the dash character at the start or end to avoid unintended range specifications). Also, if you need case to be ignored use RegexOptions.IgnoreCase:
Regex.Matches(input, pattern, RegexOptions.IgnoreCase)
If your substring is in the form of a complete string, such as "Hello this", you can easily get it into an array form for searchString in this way:
string[] searchString = substring.Split(new[] { ' ' },
StringSplitOptions.RemoveEmptyEntries);
This code will do what you want, although I suggest you modify it to fit your needs better:
string resultString = null;
try
{
resultString = Regex.Match(subjectString, "Hello[, -]*this", RegexOptions.IgnoreCase).Value;
}
catch (ArgumentException ex)
{
// Syntax error in the regular expression
}
You could do this with a single Regex but it would be quite tedious as after every character you would need to test for zero or more ignored characters. It is probably easier to strip all the ignored characters with Regex.Replace(subject, "[-,]", ""); then test if the substring is there.
Or the single Regex way
Regex.IsMatch(subject, "H[-,]*e[-,]*l[-,]*l[-,]*o[-,]* [-,]*t[-,]*h[-,]*i[-,]*s[-,]*")
Here's a non-regex way to do it using string parsing.
private string GetSubstring()
{
string searchString = "Hello, -this- is a string";
string searchStringWithoutUnwantedChars = searchString.Replace(",", "").Replace("-", "");
string desiredString = string.Empty;
if(searchStringWithoutUnwantedChars.Contains("Hello this"))
desiredString = searchString.Substring(searchString.IndexOf("Hello"), searchString.IndexOf("this") + 4);
return desiredString;
}
You could do something like this, since most all of these answer require rebuilding the string in some form.
string1 is your string you want to look through
//Create a List(Of string) that contains the ignored characters'
List<string> ignoredCharacters = new List<string>();
//Add all of the characters you wish to ignore in the method you choose
//Use a function here to get a return
public bool subStringExist(List<string> ignoredCharacters, string myString, string toMatch)
{
//Copy Your string to a temp
string tempString = myString;
bool match = false;
//Replace Everything that you don't want
foreach (string item in ignoredCharacters)
{
tempString = tempString.Replace(item, "");
}
//Check if your substring exist
if (tempString.Contains(toMatch))
{
match = true;
}
return match;
}
You could always use a combination of RegEx and string searching
public class RegExpression {
public static void Example(string input, string ignore, string find)
{
string output = string.Format("Input: {1}{0}Ignore: {2}{0}Find: {3}{0}{0}", Environment.NewLine, input, ignore, find);
if (SanitizeText(input, ignore).ToString().Contains(SanitizeText(find, ignore)))
Console.WriteLine(output + "was matched");
else
Console.WriteLine(output + "was NOT matched");
Console.WriteLine();
}
public static string SanitizeText(string input, string ignore)
{
Regex reg = new Regex("[^" + ignore + "]");
StringBuilder newInput = new StringBuilder();
foreach (Match m in reg.Matches(input))
{
newInput.Append(m.Value);
}
return newInput.ToString();
}
}
Usage would be like
RegExpression.Example("Hello, -this- is a string", "-,", "Hello this"); //Should match
RegExpression.Example("Hello, -this- is a string", "-,", "Hello this2"); //Should not match
RegExpression.Example("?A&3/3/C)412&", "&/3C\\)", "A41"); // Should match
RegExpression.Example("?A&3/3/C) 412&", "&/3C\\)", "A41"); // Should not match
RegExpression.Example("?A&3/3/C)412&", "&/3C\\)", "A3C412&"); // Should match
Output
Input: Hello, -this- is a string
Ignore: -,
Find: Hello this
was matched
Input: Hello, -this- is a string
Ignore: -,
Find: Hello this2
was NOT matched
Input: ?A&3/3/C)412&
Ignore: &/3C)
Find: A41
was matched
Input: ?A&3/3/C) 412&
Ignore: &/3C)
Find: A41
was NOT matched
Input: ?A&3/3/C)412&
Ignore: &/3C)
Find: A3C412&
was matched
I have a string that looks like this:
var expression = #"Args("token1") + Args("token2")";
I want to retrieve a collection of strings that are enclosed in Args("") in the expression.
How would I do this in C# or VB.NET?
Regex:
string expression = "Args(\"token1\") + Args(\"token2\")";
Regex r = new Regex("Args\\(\"([^\"]+)\"\\)");
List<string> tokens = new List<string>();
foreach (var match in r.Matches(expression)) {
string s = match.ToString();
int start = s.IndexOf('\"');
int end = s.LastIndexOf('\"');
tokens.add(s.Substring(start + 1, end - start - 1));
}
Non-regex (this assumes that the string in the correct format!):
string expression = "Args(\"token1\") + Args(\"token2\")";
List<string> tokens = new List<string>();
int index;
while (!String.IsNullOrEmpty(expression) && (index = expression.IndexOf("Args(\"")) >= 0) {
int start = expression.IndexOf('\"', index);
string s = expression.Substring(start + 1);
int end = s.IndexOf("\")");
tokens.Add(s.Substring(0, end));
expression = s.Substring(end + 2);
}
There is another regular expression method for accomplishing this, using lookahead and lookbehind assertions:
Regex regex = new Regex("(?<=Args\\(\").*?(?=\"\\))");
string input = "Args(\"token1\") + Args(\"token2\")";
MatchCollection matches = regex.Matches(input);
foreach (var match in matches)
{
Console.WriteLine(match.ToString());
}
This strips away the Args sections of the string, giving just the tokens.
If you want token1 and token2, you can use following regex
input=#"Args(""token1"") + Args(""token2"")"
MatchCollection matches = Regex.Matches(input,#"Args\(""([^""]+)""\)");
Sorry, If this is not what you are looking for.
if your collection looks like this:
IList<String> expression = new List<String> { "token1", "token2" };
var collection = expression.Select(s => Args(s));
As long as Args returns the same type as the queried collection type this should work okay
you can then iterate over the collection like so
foreach (var s in collection)
{
Console.WriteLine(s);
}