I have a string. I need to replace all instances of a given array of strings from this original string - how would I do that?
Currently I am using...
var inputString = "this is my original string.";
var replacement = "";
var pattern = string.Join("|", arrayOfStringsToRemove);
Regex.Replace(inputString, pattern, replacement);
This works fine, but unfortunately it breaks down when someone tries to remove a character that has a special meaning in the regex.
How should I do this? Is there a better way?
Build the pattern using Regex.Escape:
StringBuilder pattern = new StringBuilder();
foreach (string s in arrayOfStringsToRemove)
{
pattern.Append("(");
pattern.Append(Regex.Escape(s));
pattern.Append(")|");
}
Regex.Replace(inputString, pattern.ToString(0, pattern.Length - 1), // remove trailing |
replacement);
Look at Regex.Escape
You need to escape special characters with a backslash
\
Sometimes you may need to use two backslashes
\\
You need to escape characters with spacial meaning of course.
var str_to_replace = "removing \[this\]\(link\)";
Related
I have a string, for example
<#String1#> + <#String2#> , <#String3#> --<#String4#>
And I want to use regex/string manipulation to get the following result:
<#String1#>,<#String2#>,<#String3#>,<#String4#>
I don't really have any experience doing this, any tips?
There are multiple ways to do something like this, and it depends on exactly what you need. However, if you want to use a single regex operation to do it, and you only want to fix stuff that comes between the bracketed strings, then you could do this:
string input = "<#String1#> + <#String2#> , <#String3#> --<#String4#>";
string pattern = "(?<=>)[^<>]+(?=<)";
string replacement = ",";
string result = Regex.Replace(input, pattern, replacement);
The pattern uses [^<>]+ to match any non-pointy-bracket characters, but it combines it with a look-behind statement ((?<=>)) and a look-ahead statement (?=<) to make sure that it only matches text that occurs between a closing and another opening set of brackets.
If you need to remove text that comes before the first < or after the last >, or if you find the look-around statements confusing, you may want to consider simply matching the text that comes between the brackets and then loop through all the matches and build a new string yourself, rather than using the RegEx.Replace method. For instance:
string input = "sdfg<#String1#> + <#String2#> , <#String3#> --<#String4#>ag";
string pattern = #"<[^<>]+>";
List<String> values = new List<string>();
foreach (Match m in Regex.Matches(input, pattern))
values.Add(m.Value);
string result = String.Join(",", values);
Or, the same thing using LINQ:
string input = "sdfg<#String1#> + <#String2#> , <#String3#> --<#String4#>ag";
string pattern = #"<[^<>]+>";
string result = String.Join(",", Regex.Matches(input, pattern).Cast<Match>().Select(x => x.Value));
If you're just after string manipulation and don't necessarily need a regex, you could simply use the string.Replace method.
yourString = yourString.Replace("#> + <#", "#>,<#");
How can I escape certain characters in a string with a C# Regex?
This is a test for % and ' thing? -> This is a test for \% and \' thing?
resultString = Regex.Replace(subjectString,
#"(?<! # Match a position before which there is no
(?<!\\) # odd number of backlashes
\\ # (it's odd if there is one backslash,
(?:\\\\)* # followed by an even number of backslashes)
)
(?=[%']) # and which is followed by a % or a '",
#"\", RegexOptions.IgnorePatternWhitespace);
However, if you're trying to protect yourself against malevolent SQL queries, regex is not the right way to go.
var escapedString = Regex.Replace(input, #"[%']", #"\$1");
This is pretty much all you need. Inside the square brackets, you should put every character you wish to escape with a backslash, which may include the backslash character itself.
I don't think this could be done with regex in good fashion, but you can simply run a for loop:
var specialChars = new char[]{'%',....};
var stream = "";
for (int i=0;i<myStr.Length;i++)
{
if (specialChars.Contains(myStr[i])
{
stream+= '\\';
}
stream += myStr[i];
}
(1) you can use StringBuilder to prevent from too many string creation.
string myNumber = "3.44";
Regex regex1 = new Regex(".");
string[] substrings = regex1.Split(myNumber);
foreach (var substring in substrings)
{
Console.WriteLine("The string is : {0} and the length is {1}",substring, substring.Length);
}
Console.ReadLine();
I tried to split the string by ".", but it the splits return 4 empty string. Why?
. means "any character" in regular expressions. So don't split using a regex - split using String.Split:
string[] substrings = myNumber.Split('.');
If you really want to use a regex, you could use:
Regex regex1 = new Regex(#"\.");
The # makes it a verbatim string literal, to stop you from having to escape the backslash. The backslash within the string itself is an escape for the dot within the regex parser.
the easiest solution would be: string[] val = myNumber.Split('.');
. is a reserved character in regex. if you literally want to match a period, try:
Regex regex1 = new Regex(#"\.");
However, you're better off simply using myNumber.Split(".");
The dot matches a single character, without caring what that character
is. The only exception are newline characters.
Source: http://www.regular-expressions.info/dot.html
Therefore your implying in your code to split the string at each character.
Use this instead.
string substr = num.Split('.');
Keep it simple, use String.Split() method;
string[] substrings = myNumber.Split('.');
It has an other overload which allows specifying split options:
public string[] Split(
char[] separator,
StringSplitOptions options
)
You don't need regex you do that by using Split method of string object
string myNumber = "3.44";
String[] substrings = myNumber.Split(".");
foreach (var substring in substrings)
{
Console.WriteLine("The string is : {0} and the length is {1}",substring, substring.Length);
}
Console.ReadLine();
The period "." is being interpreted as any single character instead of a literal period.
Instead of using regular expressions you could just do:
string[] substrings = myNumber.Split(".");
In Regex patterns, the period character matches any single character. If you want the Regex to match the actual period character, you must escape it in the pattern, like so:
#"\."
Now, this case is somewhat simple for Regex matching; you could instead use String.Split() which will split based on the occurrence of one or more static strings or characters:
string[] substrings = myNumber.Split('.');
try
Regex regex1 = new Regex(#"\.");
EDIT: Er... I guess under a minute after Jon Skeet is not too bad, anyway...
You'll want to place an escape character before the "." - like this "\\."
"." in a regex matches any character, so if you pass 4 characters to a regex with only ".", it will return four empty strings. Check out this page for common operators.
Try
Regex regex1 = new Regex("[.]");
How to replace the below string in C#
Current:
"John K "GEN" Greg"
The Goal:
"John K \"GEN\" Greg"
This is wrong because I'm not escaping it properly:
s = s.Replace(""","\"");
What is syntax for replacing quotes with \ (slash)?
Any help would be appreciated.
Thanks
s = s.Replace("\"", "\\\"");
or
s = s.Replace(#"""", #"\""");
In the first example the " has to be escaped with a backslash as it would otherwise end the string. Likewise, in the replacement string \\ is needed to yield a single backslash by escaping the escape character.
In the second example verbatim string literals are used, they are written as #"...". In those literals no escape sequences are recognized, allowing you to write strings that contain lots of backslashes in a much cleaner way (such as regular expressions). The only escape sequence that works there is "" for a single ".
You should use a double backslash:
s = s.Replace("\"", "\\\"");
To remove ALL quotes from a string, try:
field.Value = Regex.Replace(field.Value, #"[\""]", "", RegexOptions.None);
What a pain trying to find this answer on the internet!
s = s.Replace("\"","\\\"");
What are you escaping it for? If you're going to insert it into DB, consider using prepared statements instead. If you're going to use it in your HTML output, consider using some template engine that does it for yourself instead.
Try: var result = yourString.Replace("\"", "\\\"");
string MailFrom ="aaa#my.web.pk;\"PROMMS\" ccc#my.web.pk;";
string NewMailFrom = Regex.Replace(MailFrom, "\"[^\"]*\"", string.Empty);
Results
aaa#my.web.pk;ccc#my.web.pk;
What am I doing wrong here?
string q = "john s!";
string clean = Regex.Replace(q, #"([^a-zA-Z0-9]|^\s)", string.Empty);
// clean == "johns". I want "john s";
just a FYI
string clean = Regex.Replace(q, #"[^a-zA-Z0-9\s]", string.Empty);
would actually be better like
string clean = Regex.Replace(q, #"[^\w\s]", string.Empty);
This:
string clean = Regex.Replace(dirty, "[^a-zA-Z0-9\x20]", String.Empty);
\x20 is ascii hex for 'space' character
you can add more individual characters that you want to be allowed.
If you want for example "?" to be ok in the return string add \x3f.
I got it:
string clean = Regex.Replace(q, #"[^a-zA-Z0-9\s]", string.Empty);
Didn't know you could put \s in the brackets
The following regex is for space inclusion in textbox.
Regex r = new Regex("^[a-zA-Z\\s]+");
r.IsMatch(textbox1.text);
This works fine for me.
I suspect ^ doesn't work the way you think it does outside of a character class.
What you're telling it to do is replace everything that isn't an alphanumeric with an empty string, OR any leading space. I think what you mean to say is that spaces are ok to not replace - try moving the \s into the [] class.
There appear to be two problems.
You're using the ^ outside a [] which matches the start of the line
You're not using a * or + which means you will only match a single character.
I think you want the following regex #"([^a-zA-Z0-9\s])+"
bottom regex with space, supports all keyboard letters from different culture
string input = "78-selim güzel667.,?";
Regex regex = new Regex(#"[^\w\x20]|[\d]");
var result= regex.Replace(input,"");
//selim güzel
The circumflex inside the square brackets means all characters except the subsequent range. You want a circumflex outside of square brackets.
This regex will help you to filter if there is at least one alphanumeric character and zero or more special characters i.e. _ (underscore), \s whitespace, -(hyphen)
string comparer = "string you want to compare";
Regex r = new Regex(#"^([a-zA-Z0-9]+[_\s-]*)+$");
if (!r.IsMatch(comparer))
{
return false;
}
return true;
Create a set using [a-zA-Z0-9]+ for alphanumeric characters, "+" sign (a quantifier) at the end of the set will make sure that there will be at least one alphanumeric character within the comparer.
Create another set [_\s-]* for special characters, "*" quantifier is to validate that there can be special characters within comparer string.
Pack these sets into a capture group ([a-zA-Z0-9]+[_\s-]*)+ to say that the comparer string should occupy these features.
[RegularExpression(#"^[A-Z]+[a-zA-Z""'\s-]*$")]
Above syntax also accepts space