I am a complete newbie when it comes to Regular Expressions, and was wondering if somebody could help me out. I'm not sure if using a regEx is the correct approach here, so please feel free to chime in if you have a better idea. (I will be looping thru many strings).
Basically, I'd like to find/replace on a string, wrapping the matches with {} and keeping the original case of the string.
Example:
Source: "The CAT sat on the mat."
Find/Replace: "cat"
Result: "The {CAT} sat on the mat."
I would like the find/replace to work on only the first occurance, and I also need to know whether the find/replace did indeed match or not.
I hope I've explained things clearly enough.
Thank you.
Regex theRegex =
new Regex("(" + Regex.Escape(FindReplace) + ")", RegexOptions.IgnoreCase);
theRegex.Replace(Source, "{$1}", 1);
If you want word boundary tolerance:
Regex theRegex =
(#"([\W_])(" + Regex.Escape(FindReplace) + #")([\W_])", RegexOptions.IgnoreCase)
theRegex.Replace(str, "$1{$2}$3", 1)
If you will be looping through many strings, then perhaps Regex might not be the best idea - it's a great tool, but not the fastest.
Here's a sample code that would also work:
var str = "The Cat ate a mouse";
var search = "cat";
var index = str.IndexOf(search, StringComparison.CurrentCultureIgnoreCase);
if (index == -1)
throw new Exception("String not found"); //or do something else in this case here
var newStr = str.Substring(0, index) + "{" + str.Substring(index, search.Length) + "}" + str.Substring(index + search.Length);
EDIT:
As noted in the comments, the above code has some issues.
So I decided to try and find a way to make it work without using Regex. Don't get me wrong, I love Regex as much as the next guy. I did this mostly out of curiosity. ;)
Here's what I came upon:
public static class StringExtendsionsMethods
{
public static int IndexOfUsingBoundary(this String s, String word)
{
var firstLetter = word[0].ToString();
StringBuilder sb = new StringBuilder();
bool previousWasLetterOrDigit = false;
int i = 0;
while (i < s.Length - word.Length + 1)
{
bool wordFound = false;
char c = s[i];
if (c.ToString().Equals(firstLetter, StringComparison.CurrentCultureIgnoreCase))
if (!previousWasLetterOrDigit)
if (s.Substring(i, word.Length).Equals(word, StringComparison.CurrentCultureIgnoreCase))
{
wordFound = true;
bool wholeWordFound = true;
if (s.Length > i + word.Length)
{
if (Char.IsLetterOrDigit(s[i + word.Length]))
wholeWordFound = false;
}
if (wholeWordFound)
return i;
sb.Append(word);
i += word.Length;
}
if (!wordFound)
{
previousWasLetterOrDigit = Char.IsLetterOrDigit(c);
sb.Append(c);
i++;
}
}
return -1;
}
}
But I can't take credit for this! I found this after some Googling here, on StackOverflow and then modified it. ;)
Use this method instead of the standard IndexOf in the above code.
Try this:
class Program
{
const string FindReplace = "cat";
static void Main(string[] args)
{
var input = "The CAT sat on the mat as a cat.";
var result = Regex
.Replace(
input,
"(?<=.*)" + FindReplace + "(?=.*)",
m =>
{
return "{" + m.Value.ToUpper() + "}";
},
RegexOptions.IgnoreCase);
Console.WriteLine(result);
}
}
Hello im a bit stuck i dont know how to find the third longest word in a string, i have got my code to find the longest but i cant manage to get it to find the third longest. any help?
public void longestWord()
{
string sentance, word;
word = " ";
char[] a = new char[] { ' ' };
sentance = textBox1.Text; //<--string here
foreach (string s1 in sentance.Split(a))
{
if (word.Length < s1.Length)
{
word = s1;
}
}
label9.Text = ("The longest word is " + word + " and its length is " + word.Length + " characters long");
}
P.S an example of the string im testing is:
1.
DarkN3ss is my most experienced provider of Windows based business solutions. I focus on delivering my business value in best possible understanding of this technologies and directions.
DarkN3ss recognising me as an “elite business partner” for implementing solutions based on my capabilities and experience with Windows and Linux products.
how about using linq?
sentance.Split(' ').OrderByDescending(w => w.Length).Skip(2).FirstOrDefault()
in a function :
public void nthLongestWord(int index = 0)
{
string word = null;
if(index <= 0)
{
word = sentance.Split(' ').OrderByDescending(w => w.Length).FirstOrDefault();
}
else
{
word = sentance.Split(' ').OrderByDescending(w => w.Length).Skip(index - 1).FirstOrDefault();
}
if(!string.IsNullOrWhitespace(word))
{
label9.Text = ("The longest word is " + word + " and its length is " + word.Length + " characters long");
}
else
{
// display something else?
}
}
Solution: To get all the third largest words
string[] splitStr = sentence.Split(' ');
if (splitStr.Length > 2)
{
List<int> allLengths = splitStr.Select(x => x.Length).Distinct().ToList();
int thirdLargestWordLength = allLengths.OrderByDescending(x => x)
.Skip(2).Distinct().Take(1).FirstOrDefault();
if (splitStr[0].Length != thirdLargestWordLength &&
splitStr[1].Length != thirdLargestWordLength)
{
string[] theThirdLargestWords = splitStr.Where(x => x.Length == thirdLargestWordLength)
.ToArray();
if (theThirdLargestWords.Length == 1)
{
label9.Text = "The third longest word is " + theThirdLargestWords[0];
}
else
{
string words = "";
for (int i = 0; i < theThirdLargestWords.Length; i++)
{
if (i == 0)
{
words = theThirdLargestWords[i];
}
//else if ((i + 1) == theThirdLargestWords.Length)
//{
// words += " and " + theThirdLargestWords[i];
//}
else
{
words += ", " + theThirdLargestWords[i];
}
}
label9.Text = "The third longest words are " + words;
}
}
}
I commented out the "and" part as i'm not sure if you want that in your string. I also added the first if statement so you don't get an error if you have less then 3 words.
If you'd like to make minimal changes to your current code, then what you should do is store the three longest words (i.e., instead of word, have word1, word2, and word3, or an array if you'd prefer).
Then, in your if statement, set word3=word2, word2=word1, and word1=s1.
That way, the third largest word will end up in word3.
Not the most efficient, but you'll be able to keep your current code, to a degree.
If you feel confortable using a temporary array, you should copy your words there, sort them and take the 3rd longest one.
This might have compile error, but just to give you an idea.
var words = sentence.split();
words.OrderBy (w => w.length ).ToArray ()[2]
I need to take a sentence in that is all on one line with no spaces and each new word has a captial letter EX. "StopAndSmellTheRoses" and then convert it to "Stop and smell the roses" This is my function that I have but I keep getting an argument out of range error on the insert method. Thanks for any help in advance.
private void FixSentence()
{
// String to hold our sentence in trim at same time
string sentence = txtSentence.Text.Trim();
// loop through the string
for (int i = 0; i < sentence.Length; i++)
{
if (char.IsUpper(sentence, i) & sentence[i] != 0)
{
// Change to lowercase
char.ToLower(sentence[i]);
// Insert space behind the character
// This is where I get my error
sentence = sentence.Insert(i-1, " ");
}
}
// Show our Fixed Sentence
lblFixed.Text = "";
lblFixed.Text = "Fixed: " + sentence;
}
The best way to build up a String in this manner is to use a StringBuilder instance.
var sentence = txtSentence.Text.Trim();
var builder = new StringBuilder();
foreach (var cur in sentence) {
if (Char.IsUpper(cur) && builder.Length != 0) {
builder.Append(' ');
}
builder.Append(cur);
}
// Show our Fixed Sentence
lblFixed.Text = "";
lblFixed.Text = "Fixed: " + builder.ToString();
Using the Insert method creates a new string instance every time resulting in a lot of needlessly allocated values. The StringBuilder though won't actually allocate a String until you call the ToString method.
You can't modify the sentence variable in the loop that is going through it.
Instead, you need to have a second string variable that you append all of the found words.
Here is the answer
var finalstr = Regex.Replace(
"StopAndSmellTheRoses",
"(?<=[a-z])(?<x>[A-Z])|(?<=.)(?<x>[A-Z])(?=[a-z])|(?<=[^0-9])(?<x>[0-9])(?=.)",
me => " " + me.Value.ToLower()
);
will output
Stop and smell the roses
Another version:
public static class StringExtensions
{
public static string FixSentence(this string instance)
{
char[] capitals = Enumerable.Range(65, 26).Select(x => (char)x).ToArray();
string[] words = instance.Split(capitals);
string result = string.Join(' ', words);
return char.ToUpper(result[0]) + result.Substring(1).ToLower();
}
}
How can the first letter in a text be set to capital?
Example:
it is a text. = It is a text.
public static string ToUpperFirstLetter(this string source)
{
if (string.IsNullOrEmpty(source))
return string.Empty;
// convert to char array of the string
char[] letters = source.ToCharArray();
// upper case the first char
letters[0] = char.ToUpper(letters[0]);
// return the array made of the new char array
return new string(letters);
}
It'll be something like this:
// precondition: before must not be an empty string
String after = before.Substring(0, 1).ToUpper() + before.Substring(1);
polygenelubricants' answer is fine for most cases, but you potentially need to think about cultural issues. Do you want this capitalized in a culture-invariant way, in the current culture, or a specific culture? It can make a big difference in Turkey, for example. So you may want to consider:
CultureInfo culture = ...;
text = char.ToUpper(text[0], culture) + text.Substring(1);
or if you prefer methods on String:
CultureInfo culture = ...;
text = text.Substring(0, 1).ToUpper(culture) + text.Substring(1);
where culture might be CultureInfo.InvariantCulture, or the current culture etc.
For more on this problem, see the Turkey Test.
If you are using C# then try this code:
Microsoft.VisualBasic.StrConv(sourceString, Microsoft.VisualBasic.vbProperCase)
I use this variant:
private string FirstLetterCapital(string str)
{
return Char.ToUpper(str[0]) + str.Remove(0, 1);
}
If you are sure that str variable is valid (never an empty-string or null), try:
str = Char.ToUpper(str[0]) + str[1..];
Unlike the other solutions that use Substring, this one does not do additional string allocations. This example basically concatenates char with ReadOnlySpan<char>.
I realize this is an old post, but I recently had this problem and solved it with the following method.
private string capSentences(string str)
{
string s = "";
if (str[str.Length - 1] == '.')
str = str.Remove(str.Length - 1, 1);
char[] delim = { '.' };
string[] tokens = str.Split(delim);
for (int i = 0; i < tokens.Length; i++)
{
tokens[i] = tokens[i].Trim();
tokens[i] = char.ToUpper(tokens[i][0]) + tokens[i].Substring(1);
s += tokens[i] + ". ";
}
return s;
}
In the sample below clicking on the button executes this simple code outBox.Text = capSentences(inBox.Text.Trim()); which pulls the text from the upper box and puts it in the lower box after the above method runs on it.
Take the first letter out of the word and then extract it to the other string.
strFirstLetter = strWord.Substring(0, 1).ToUpper();
strFullWord = strFirstLetter + strWord.Substring(1);
text = new String(
new [] { char.ToUpper(text.First()) }
.Concat(text.Skip(1))
.ToArray()
);
this functions makes capital the first letter of all words in a string
public static string FormatSentence(string source)
{
var words = source.Split(' ').Select(t => t.ToCharArray()).ToList();
words.ForEach(t =>
{
for (int i = 0; i < t.Length; i++)
{
t[i] = i.Equals(0) ? char.ToUpper(t[i]) : char.ToLower(t[i]);
}
});
return string.Join(" ", words.Select(t => new string(t)));;
}
string str = "it is a text";
// first use the .Trim() method to get rid of all the unnecessary space at the begining and the end for exemple (" This string ".Trim() is gonna output "This string").
str = str.Trim();
char theFirstLetter = str[0]; // this line is to take the first letter of the string at index 0.
theFirstLetter.ToUpper(); // .ToTupper() methode to uppercase the firstletter.
str = theFirstLetter + str.substring(1); // we add the first letter that we uppercased and add the rest of the string by using the str.substring(1) (str.substring(1) to skip the first letter at index 0 and only print the letters from the index 1 to the last index.)
Console.WriteLine(str); // now it should output "It is a text"
static String UppercaseWords(String BadName)
{
String FullName = "";
if (BadName != null)
{
String[] FullBadName = BadName.Split(' ');
foreach (string Name in FullBadName)
{
String SmallName = "";
if (Name.Length > 1)
{
SmallName = char.ToUpper(Name[0]) + Name.Substring(1).ToLower();
}
else
{
SmallName = Name.ToUpper();
}
FullName = FullName + " " + SmallName;
}
}
FullName = FullName.Trim();
FullName = FullName.TrimEnd();
FullName = FullName.TrimStart();
return FullName;
}
string Input = " it is my text";
Input = Input.TrimStart();
//Create a char array
char[] Letters = Input.ToCharArray();
//Make first letter a capital one
string First = char.ToUpper(Letters[0]).ToString();
//Concatenate
string Output = string.Concat(First,Input.Substring(1));
Try this code snippet:
char nm[] = "this is a test";
if(char.IsLower(nm[0])) nm[0] = char.ToUpper(nm[0]);
//print result: This is a test
How can I replace multiple spaces in a string with only one space in C#?
Example:
1 2 3 4 5
would be:
1 2 3 4 5
I like to use:
myString = Regex.Replace(myString, #"\s+", " ");
Since it will catch runs of any kind of whitespace (e.g. tabs, newlines, etc.) and replace them with a single space.
string sentence = "This is a sentence with multiple spaces";
RegexOptions options = RegexOptions.None;
Regex regex = new Regex("[ ]{2,}", options);
sentence = regex.Replace(sentence, " ");
string xyz = "1 2 3 4 5";
xyz = string.Join( " ", xyz.Split( new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries ));
I think Matt's answer is the best, but I don't believe it's quite right. If you want to replace newlines, you must use:
myString = Regex.Replace(myString, #"\s+", " ", RegexOptions.Multiline);
Another approach which uses LINQ:
var list = str.Split(' ').Where(s => !string.IsNullOrWhiteSpace(s));
str = string.Join(" ", list);
It's much simpler than all that:
while(str.Contains(" ")) str = str.Replace(" ", " ");
Regex can be rather slow even with simple tasks. This creates an extension method that can be used off of any string.
public static class StringExtension
{
public static String ReduceWhitespace(this String value)
{
var newString = new StringBuilder();
bool previousIsWhitespace = false;
for (int i = 0; i < value.Length; i++)
{
if (Char.IsWhiteSpace(value[i]))
{
if (previousIsWhitespace)
{
continue;
}
previousIsWhitespace = true;
}
else
{
previousIsWhitespace = false;
}
newString.Append(value[i]);
}
return newString.ToString();
}
}
It would be used as such:
string testValue = "This contains too much whitespace."
testValue = testValue.ReduceWhitespace();
// testValue = "This contains too much whitespace."
myString = Regex.Replace(myString, " {2,}", " ");
For those, who don't like Regex, here is a method that uses the StringBuilder:
public static string FilterWhiteSpaces(string input)
{
if (input == null)
return string.Empty;
StringBuilder stringBuilder = new StringBuilder(input.Length);
for (int i = 0; i < input.Length; i++)
{
char c = input[i];
if (i == 0 || c != ' ' || (c == ' ' && input[i - 1] != ' '))
stringBuilder.Append(c);
}
return stringBuilder.ToString();
}
In my tests, this method was 16 times faster on average with a very large set of small-to-medium sized strings, compared to a static compiled Regex. Compared to a non-compiled or non-static Regex, this should be even faster.
Keep in mind, that it does not remove leading or trailing spaces, only multiple occurrences of such.
This is a shorter version, which should only be used if you are only doing this once, as it creates a new instance of the Regex class every time it is called.
temp = new Regex(" {2,}").Replace(temp, " ");
If you are not too acquainted with regular expressions, here's a short explanation:
The {2,} makes the regex search for the character preceding it, and finds substrings between 2 and unlimited times.
The .Replace(temp, " ") replaces all matches in the string temp with a space.
If you want to use this multiple times, here is a better option, as it creates the regex IL at compile time:
Regex singleSpacify = new Regex(" {2,}", RegexOptions.Compiled);
temp = singleSpacify.Replace(temp, " ");
You can simply do this in one line solution!
string s = "welcome to london";
s.Replace(" ", "()").Replace(")(", "").Replace("()", " ");
You can choose other brackets (or even other characters) if you like.
no Regex, no Linq... removes leading and trailing spaces as well as reducing any embedded multiple space segments to one space
string myString = " 0 1 2 3 4 5 ";
myString = string.Join(" ", myString.Split(new char[] { ' ' },
StringSplitOptions.RemoveEmptyEntries));
result:"0 1 2 3 4 5"
// Mysample string
string str ="hi you are a demo";
//Split the words based on white sapce
var demo= str .Split(' ').Where(s => !string.IsNullOrWhiteSpace(s));
//Join the values back and add a single space in between
str = string.Join(" ", demo);
// output: string str ="hi you are a demo";
Consolodating other answers, per Joel, and hopefully improving slightly as I go:
You can do this with Regex.Replace():
string s = Regex.Replace (
" 1 2 4 5",
#"[ ]{2,}",
" "
);
Or with String.Split():
static class StringExtensions
{
public static string Join(this IList<string> value, string separator)
{
return string.Join(separator, value.ToArray());
}
}
//...
string s = " 1 2 4 5".Split (
" ".ToCharArray(),
StringSplitOptions.RemoveEmptyEntries
).Join (" ");
I just wrote a new Join that I like, so I thought I'd re-answer, with it:
public static string Join<T>(this IEnumerable<T> source, string separator)
{
return string.Join(separator, source.Select(e => e.ToString()).ToArray());
}
One of the cool things about this is that it work with collections that aren't strings, by calling ToString() on the elements. Usage is still the same:
//...
string s = " 1 2 4 5".Split (
" ".ToCharArray(),
StringSplitOptions.RemoveEmptyEntries
).Join (" ");
Many answers are providing the right output but for those looking for the best performances, I did improve Nolanar's answer (which was the best answer for performance) by about 10%.
public static string MergeSpaces(this string str)
{
if (str == null)
{
return null;
}
else
{
StringBuilder stringBuilder = new StringBuilder(str.Length);
int i = 0;
foreach (char c in str)
{
if (c != ' ' || i == 0 || str[i - 1] != ' ')
stringBuilder.Append(c);
i++;
}
return stringBuilder.ToString();
}
}
Use the regex pattern
[ ]+ #only space
var text = Regex.Replace(inputString, #"[ ]+", " ");
I know this is pretty old, but ran across this while trying to accomplish almost the same thing. Found this solution in RegEx Buddy. This pattern will replace all double spaces with single spaces and also trim leading and trailing spaces.
pattern: (?m:^ +| +$|( ){2,})
replacement: $1
Its a little difficult to read since we're dealing with empty space, so here it is again with the "spaces" replaced with a "_".
pattern: (?m:^_+|_+$|(_){2,}) <-- don't use this, just for illustration.
The "(?m:" construct enables the "multi-line" option. I generally like to include whatever options I can within the pattern itself so it is more self contained.
I can remove whitespaces with this
while word.contains(" ") //double space
word = word.Replace(" "," "); //replace double space by single space.
word = word.trim(); //to remove single whitespces from start & end.
Without using regular expressions:
while (myString.IndexOf(" ", StringComparison.CurrentCulture) != -1)
{
myString = myString.Replace(" ", " ");
}
OK to use on short strings, but will perform badly on long strings with lots of spaces.
try this method
private string removeNestedWhitespaces(char[] st)
{
StringBuilder sb = new StringBuilder();
int indx = 0, length = st.Length;
while (indx < length)
{
sb.Append(st[indx]);
indx++;
while (indx < length && st[indx] == ' ')
indx++;
if(sb.Length > 1 && sb[0] != ' ')
sb.Append(' ');
}
return sb.ToString();
}
use it like this:
string test = removeNestedWhitespaces("1 2 3 4 5".toCharArray());
Here is a slight modification on Nolonar original answer.
Checking if the character is not just a space, but any whitespace, use this:
It will replace any multiple whitespace character with a single space.
public static string FilterWhiteSpaces(string input)
{
if (input == null)
return string.Empty;
var stringBuilder = new StringBuilder(input.Length);
for (int i = 0; i < input.Length; i++)
{
char c = input[i];
if (i == 0 || !char.IsWhiteSpace(c) || (char.IsWhiteSpace(c) &&
!char.IsWhiteSpace(strValue[i - 1])))
stringBuilder.Append(c);
}
return stringBuilder.ToString();
}
How about going rogue?
public static string MinimizeWhiteSpace(
this string _this)
{
if (_this != null)
{
var returned = new StringBuilder();
var inWhiteSpace = false;
var length = _this.Length;
for (int i = 0; i < length; i++)
{
var character = _this[i];
if (char.IsWhiteSpace(character))
{
if (!inWhiteSpace)
{
inWhiteSpace = true;
returned.Append(' ');
}
}
else
{
inWhiteSpace = false;
returned.Append(character);
}
}
return returned.ToString();
}
else
{
return null;
}
}
Mix of StringBuilder and Enumerable.Aggregate() as extension method for strings:
using System;
using System.Linq;
using System.Text;
public static class StringExtension
{
public static string CondenseSpaces(this string s)
{
return s.Aggregate(new StringBuilder(), (acc, c) =>
{
if (c != ' ' || acc.Length == 0 || acc[acc.Length - 1] != ' ')
acc.Append(c);
return acc;
}).ToString();
}
public static void Main()
{
const string input = " (five leading spaces) (five internal spaces) (five trailing spaces) ";
Console.WriteLine(" Input: \"{0}\"", input);
Console.WriteLine("Output: \"{0}\"", StringExtension.CondenseSpaces(input));
}
}
Executing this program produces the following output:
Input: " (five leading spaces) (five internal spaces) (five trailing spaces) "
Output: " (five leading spaces) (five internal spaces) (five trailing spaces) "
Old skool:
string oldText = " 1 2 3 4 5 ";
string newText = oldText
.Replace(" ", " " + (char)22 )
.Replace( (char)22 + " ", "" )
.Replace( (char)22 + "", "" );
Assert.That( newText, Is.EqualTo( " 1 2 3 4 5 " ) );
You can create a StringsExtensions file with a method like RemoveDoubleSpaces().
StringsExtensions.cs
public static string RemoveDoubleSpaces(this string value)
{
Regex regex = new Regex("[ ]{2,}", RegexOptions.None);
value = regex.Replace(value, " ");
// this removes space at the end of the value (like "demo ")
// and space at the start of the value (like " hi")
value = value.Trim(' ');
return value;
}
And then you can use it like this:
string stringInput =" hi here is a demo ";
string stringCleaned = stringInput.RemoveDoubleSpaces();
I looked over proposed solutions, could not find the one that would handle mix of white space characters acceptable for my case, for example:
Regex.Replace(input, #"\s+", " ") - it will eat your line breaks, if they are mixed with spaces, for example \n \n sequence will be replaced with
Regex.Replace(source, #"(\s)\s+", "$1") - it will depend on whitespace first character, meaning that it again might eat your line breaks
Regex.Replace(source, #"[ ]{2,}", " ") - it won't work correctly when there's mix of whitespace characters - for example "\t \t "
Probably not perfect, but quick solution for me was:
Regex.Replace(input, #"\s+",
(match) => match.Value.IndexOf('\n') > -1 ? "\n" : " ", RegexOptions.Multiline)
Idea is - line break wins over the spaces and tabs.
This won't handle windows line breaks correctly, but it would be easy to adjust to work with that too, don't know regex that well - may be it is possible to fit into single pattern.
The following code remove all the multiple spaces into a single space
public string RemoveMultipleSpacesToSingle(string str)
{
string text = str;
do
{
//text = text.Replace(" ", " ");
text = Regex.Replace(text, #"\s+", " ");
} while (text.Contains(" "));
return text;
}