How to check if a string contains only # [duplicate] - c#

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Check If String Contains All "?"
(8 answers)
Closed 9 years ago.
I have a string like "# # # # #"
another string like "123 # abc # xyz"
I need to check if the string contains only # .How to achieve this.
I tried using contains ,but this does not work .

Providing that the String is not null, the possible solution can be:
String text = "123#abc#xyz";
Boolean result = text.All((x) => x == '#');
In case the white spaces should be ignored (e.g. "# # # # #" considered being the right string)
String text = "123#abc#xyz";
Boolean result = text.All((x) => x == '#' || Char.IsWhiteSpace(x));

bool IsSharpOnly(string str)
for(int i = 0; i < str.Length ; i++)
if (str[i] != '#')
return false;
return true;

Another solution with a Regex:
Regex r = new Regex("^#+$");
bool b1 = r.IsMatch("asdas#asdas");
bool b2 = r.IsMatch("#####");
Was not sure if white space should be ignored or not, if so:
Regex r = new Regex("^[\\s*#+]+$");

With a regular expression?
Like this: "([0-9]+)|([a-z]+)"
you can check if the input string does not match.
For instance for the string contains '#' only:
String text = "123#abc#xyz";
Boolean result = Regex.Match(text, "^#*$").Success;

Try this,
string ss = "##g#";
if ((ss.Split('#').Length - 1).Equals(ss.Length))
//Contains only #

You can also try this:
private bool CheckIfStringContainsOnlyHash(string value)
return !value.Where(a => !string.IsNullOrWhiteSpace(a.ToString()) && a != '#').Select(a => true).FirstOrDefault();

Try the below code
string txt = "123#abc#xyz";
if (!txt.Any((X) => X != '#'))
//Contains only '#'

Dmitry's example is probably the most elegant, but something like this could work too (again assuming the input has been null checked):
string test = "#####";
return test.Replace("#", "").Length == 0;
EDIT: picking up on the discussion about ignoring whitespace too, we could use:
string test = "#####";
return String.IsNullOrWhiteSpace(test.Replace("#", ""));

this is also a solution
String data= "###########";
bool isAllSame = data.All(d => d == '#');
// code when string contain only #


Get Expression in Named Capture

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;
else if (sThis == ")" && sPrev != #"\")
else if (sThis == "(" && sPrev != #"\")
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)
.Select(mt => mt.Groups[0].Value)
returns one item of
While the data such as (?<FileMonth>[^\s]+)\s+(?<FileYear>\d{4}) Records\.xlsx would return two matches:
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:
or more concisely...
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}

Comparing string

Is there any method that allow us to return true if string a likes string b formality?
"12:2".Like("*:*") = true
"what is your name?".Like("*is*name*?")=true
You can use this following function using Regular Expression
Regex.IsMatch("string", "your expression")
Instance following line should return true:
Regex.IsMatch("12:2", "/[0-9]{2,}:[0-9]{1,}/")
Note: This way you have to create exp every time for different format
You can use the following method to check whether a given string matches a DOS like pattern with wildcards (i.e. a pattern that denotes one character with '?' and zero or more characters with '*'):
public static bool IsMatch(string str, string pattern)
string regexString = "^" + Regex.Escape(pattern).Replace("\\*", ".*").Replace("\\?", ".") + "$";
Regex regex = new Regex(regexString);
return regex.IsMatch(regexString);
You can call it like this:
bool match = IsMatch("what is your name?", "*is*name*?"); // Returns true
You can use the following not-optimized method. The function may does not take into account some cases, but i think it gives you a point to start from.
Another possible solution is to you Regular Expressions
public static bool Like(string pattern, string str)
string[] words = pattern.Split('*').Where(w => w.Trim() != string.Empty).ToArray();
List<int> indeces = new List<int>();
for (int i = 0, l = words.Length; i < l; i++)
int wordIndex = str.IndexOf(words[i], StringComparison.OrdinalIgnoreCase);
if (wordIndex == -1)
return false;
List<int> sortedIndeces = indeces.ToList();
for (int i = 0, l = sortedIndeces.Count; i < l; i++)
if (sortedIndeces[i] != indeces[i]) return false;
return true;
Good Luck

Retrieve String Containing Specific substring C#

I am having an output in string format like following :
"ABCDED 0000A1.txt PQRSNT 12345"
I want to retreieve substring(s) having .txt in above string. e.g. For above it should return 0000A1.txt.
You can either split the string at whitespace boundaries like it's already been suggested or repeatedly match the same regex like this:
var input = "ABCDED 0000A1.txt PQRSNT 12345 THE.txt FOO";
var match = Regex.Match (input, #"\b([\w\d]+\.txt)\b");
while (match.Success) {
Console.WriteLine ("TEST: {0}", match.Value);
match = match.NextMatch ();
Split will work if it the spaces are the seperator. if you use oter seperators you can add as needed
string input = "ABCDED 0000A1.txt PQRSNT 12345";
string filename = input.Split(' ').FirstOrDefault(f => System.IO.Path.HasExtension(f));
filname = "0000A1.txt" and this will work for any extension
You may use c#, regex and pattern, match :)
Here is the code, plug it in try. Please comment.
string test = "afdkljfljalf dkfjd.txt lkjdfjdl";
string ffile = Regex.Match(test, #"\([a-z0-9])+.txt").Groups[1].Value;
Reference: regexp
I did something like this:
string subString = "";
char period = '.';
char[] chArString;
int iSubStrIndex = 0;
if (myString != null)
chArString = new char[myString.Length];
chArString = myString.ToCharArray();
for (int i = 0; i < myString.Length; i ++)
if (chArString[i] == period)
iSubStrIndex = i;
substring = myString.Substring(iSubStrIndex);
Hope that helps.
First split your string in array using
char[] whitespace = new char[] { ' ', '\t' };
string[] ssizes = myStr.Split(whitespace);
Then find .txt in array...
// Find first element starting with .txt.
string value1 = Array.Find(array1,
element => element.Contains(".txt", StringComparison.Ordinal));
Now your value1 will have the "0000A1.txt"
Happy coding.

Get String (Text) before next upper letter

I have the following:
string test = "CustomerNumber";
string test2 = "CustomerNumberHello";
the result should be:
string result = "Customer";
The first word from the string is the result, the first word goes until the first uppercase letter, here 'N'
I already tried some things like this:
var result = string.Concat(s.Select(c => char.IsUpper(c) ? " " + c.ToString() : c.ToString()))
But without success, hope someone could offer me a small and clean solution (without RegEx).
The following should work:
var result = new string(
test.TakeWhile((c, index) => index == 0 || char.IsLower(c)).ToArray());
You could just go through the string to see which values (ASCII) are below 97 and remove the end. Not the prettiest or LINQiest way, but it works...
string test2 = "CustomerNumberHello";
for (int i = 1; i < test2.Length; i++)
if (test2[i] < 97)
test2 = test2.Remove(i, test2.Length - i);
Console.WriteLine(test2); // Prints Customer
Try this
private static string GetFirstWord(string source)
return source.Substring(0, source.IndexOfAny("ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToArray(), 1));
Z][a-z]+ regex it will split the string to string that start with big letters her is an example
regex = "[A-Z][a-z]+";
MatchCollection mc = Regex.Matches(richTextBox1.Text, regex);
foreach (Match match in mc)
if (!match.ToString().Equals(""))
Console.writln(match.ToString() + "\n");
I have tested, this works:
string cust = "CustomerNumberHello";
string[] str = System.Text.RegularExpressions.Regex.Split(cust, #"[a-z]+");
string str2 = cust.Remove(cust.IndexOf(str[1], 1));

Find substring ignoring specified characters

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.
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:
An here are some tests:
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, "-");
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;
if (s[i] == value[matches])
else if (ignoreChars != null && ignoreChars.Contains(s[i]))
startIndex = -1;
matches = 0;
length = 0;
found = (matches == value.Length);
if (found)
result = s.Substring(startIndex, length);
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);
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))
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[] { ' ' },
This code will do what you want, although I suggest you modify it to fit your needs better:
string resultString = null;
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");
Console.WriteLine(output + "was NOT matched");
public static string SanitizeText(string input, string ignore)
Regex reg = new Regex("[^" + ignore + "]");
StringBuilder newInput = new StringBuilder();
foreach (Match m in reg.Matches(input))
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
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