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Convert special character in string into a char

I have this string:
string specialCharacterString = #"\n";
where "\n" is the new line special character.
Is it possible convert/assign that string (of two characters) into a (single) char. How do I do something like:
char specialCharacter = Parse(specialCharacterString);
Where specialCharacter value would be equal to \n
Is there anything in dotnet that would parse the string for me or must I use if or switch the string (the string can contain any special character) to accomplish what I want. Note that char.Parse(string) cannot handle special characters and thinks the string above is actually two characters.

Maybe I am oversimplifying but can't you just do the following:
txtString.Replace("\n", "$");
It is technically a string to string replacement but would be string to char...
You can always cast it to a char since you know what char you are replacing the string with.

Not sure, what business need it is, but if you need parsing C# in C# you can use some tools like Antlr, which supports C# grammar (https://github.com/antlr/grammars-v4/)
I don't think there is any ready tool designed just for strings

Try use Regex.Unescape(specialCharacterString);
It will return the new string with escape characters.
For example:
var literalStringWithEscapeCharacters = #"Hello\tWorld";
var stringWithEscapeCharacters = Regex.Unescape(literalStringWithEscapeCharacters);
Console.WriteLine(stringWithEscapeCharacters);
Will print: Hello World
Instead of: Hello\tWorld
Then you can find escape characters in stringWithEscapeCharacters like this:
var escapeChars= new [] { '\n' };
var characters = stringWithEscapeCharacters.Where(c => escapeChars.Contains(c)).ToList();
All escape characters described here:
https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/strings/#string-escape-sequences

grab text between two patern

Check the code bellow. I want to grab everything between this id="a-popover-sp-info-popover- until ". I already tried to use following Regex.Match formula but there is syntax error. Its not valid in c#. How can i do this in proper way. My goal is to grab ABC123 text.
string foo = #id="a-popover-sp-info-popover-ABC123";
string output = Regex.Match(foo, #"id="a-popover-sp-info-popover-(.*)"").Groups[1].Value;
i need to grab only text: ABC123

since your pattern is so rigid, actually the string.Split method could also do the trick:
string output1 = foo.Split(new string[] {"info-popover-"}, StringSplitOptions.RemoveEmptyEntries)
.Last()
.TrimEnd('"');
Console.WriteLine(output1);
Output:
ABC123

You have to make sure to surround your strings with quotation marks ".
If you want to have quotation marks inside of your string you have to escape them with a backslash:
string foo = "id=\"a-popover-sp-info-popover-ABC123\"";
string output = Regex.Match(foo, "id=\"a-popover-sp-info-popover-(.*)\"").Groups[1].Value;

string pattern = "id=\"a-popover-sp-info-popover-[A-Z]{3}[1-9]{3}\"";
string input = "id=\"a-popover-sp-info-popover-ABC123\"";
Match m = Regex.Match(input, pattern);
if (m.Success) Console.WriteLine("Found '{0}'", m.Value);

How to detect SUB character and remove it from a text file in C#?

I am writing a program to process special text files. Some of these text files end with a SUB character (a substitute character. It may be 0x1A.) How do I detect this character and remove it from the text file using C#?

If it's really 0x1A in the binary data, and if you're reading it as an ASCII or UTF-8 file, it should end up as U+001A when read in .NET. So you may be able to write something like:
string text = File.ReadAllText("file.txt");
text = text.Replace("\u001a", "");
File.WriteAllText("file.txt", text);
Note that the "\u001a" part is a string consisting of a single character: \uxxxx is an escape sequence for a single UTF-16 code point with the given Unicode value expressed in hex.

The easiest answer would probably be a Regex:
public static string RemoveAll(this string input, char toRemove)
{
//produces a pattern like "\x1a+" which will match any occurrence
//of one or more of the character with that hex value
var pattern = #"\x" + ((int)toRemove).ToString("x") + "+";
return Regex.Replace(input, pattern, String.Empty);
}
//usage
var cleanString = dirtyString.RemoveAll((char)0x1a);
Yes, you could just pass in the int, but that requires knowing the integer value of the character. using a char as a parameter allows you to specify a literal or char variable with less muck.

C# has a method to detect control characters (including SUB).
See msdn : https://msdn.microsoft.com/en-us/library/9s05w2k9(v=vs.110).aspx

You could also try something like this it should work
using (FileStream f = File.OpenRead("path\\file")) //Your filename + extension
{
using (StreamReader sr = new StreamReader(f))
{
string text = sr.ReadToEnd();
text = text.Replace("\u001a", string.Empty);
}
}

C# regular expression to find custom markers and take content

I have a string:
productDescription
In it are some custom tags such as:
[MM][/MM]
For example the string might read:
This product is [MM]1000[/MM] long
Using a regular expression how can I find those MM tags, take the content of them and replace everything with another string? So for example the output should be:
This product is 10 cm long

I think you'll need to pass a delegate to the regex for that.
Regex theRegex = new Regex(#"\[MM\](\d+)\[/MM\]");
text = theRegex.Replace(text, delegate(Match thisMatch)
{
int mmLength = Convert.ToInt32(thisMatch.Groups[1].Value);
int cmLength = mmLength / 10;
return cmLength.ToString() + "cm";
});

Using RegexDesigner.NET:
using System.Text.RegularExpressions;
// Regex Replace code for C#
void ReplaceRegex()
{
// Regex search and replace
RegexOptions options = RegexOptions.None;
Regex regex = new Regex(#"\[MM\](?<value>.*)\[\/MM\]", options);
string input = #"[MM]1000[/MM]";
string replacement = #"10 cm";
string result = regex.Replace(input, replacement);
// TODO: Do something with result
System.Windows.Forms.MessageBox.Show(result, "Replace");
}
Or if you want the orginal text back in the replacement:
Regex regex = new Regex(#"\[MM\](?<theText>.*)\[\/MM\]", options);
string replacement = #"${theText} cm";

A regex like this
\[(\w+)\](\d+)\[\/\w+\]
will find and collect the units (like MM) and the values (like 1000). That would at least allow you to use the pairs of parts intelligently to do the conversion. You could then put the replacement string together, and do a straightforward string replacement, because you know the exact string you're replacing.
I don't think you can do a simple RegEx.Replace, because you don't know the replacement string at the point you do the search.

Regex rex = new Regex(#"\[MM\]([0-9]+)\[\/MM\]");
string s = "This product is [MM]1000[/MM] long";
MatchCollection mc = rex.Matches(s);
Will match only integers.
mc[n].Groups[1].Value;
will then give the numeric part of nth match.

Strip double quotes from a string in .NET

I'm trying to match on some inconsistently formatted HTML and need to strip out some double quotes.
Current:
<input type="hidden">
The Goal:
<input type=hidden>
This is wrong because I'm not escaping it properly:
s = s.Replace(""","");
This is wrong because there is not blank character character (to my knowledge):
s = s.Replace('"', '');
What is syntax / escape character combination for replacing double quotes with an empty string?

I think your first line would actually work but I think you need four quotation marks for a string containing a single one (in VB at least):
s = s.Replace("""", "")
for C# you'd have to escape the quotation mark using a backslash:
s = s.Replace("\"", "");

I didn't see my thoughts repeated already, so I will suggest that you look at string.Trim in the Microsoft documentation for C# you can add a character to be trimmed instead of simply trimming empty spaces:
string withQuotes = "\"hellow\"";
string withOutQotes = withQuotes.Trim('"');
should result in withOutQuotes being "hello" instead of ""hello""

s = s.Replace("\"", "");
You need to use the \ to escape the double quote character in a string.

You can use either of these:
s = s.Replace(#"""","");
s = s.Replace("\"","");
...but I do get curious as to why you would want to do that? I thought it was good practice to keep attribute values quoted?

s = s.Replace("\"",string.Empty);

c#: "\"", thus s.Replace("\"", "")
vb/vbs/vb.net: "" thus s.Replace("""", "")

If you only want to strip the quotes from the ends of the string (not the middle), and there is a chance that there can be spaces at either end of the string (i.e. parsing a CSV format file where there is a space after the commas), then you need to call the Trim function twice...for example:
string myStr = " \"sometext\""; //(notice the leading space)
myStr = myStr.Trim('"'); //(would leave the first quote: "sometext)
myStr = myStr.Trim().Trim('"'); //(would get what you want: sometext)

You have to escape the double quote with a backslash.
s = s.Replace("\"","");

s = s.Replace(#"""", "");

This worked for me
//Sentence has quotes
string nameSentence = "Take my name \"Wesley\" out of quotes";
//Get the index before the quotes`enter code here`
int begin = nameSentence.LastIndexOf("name") + "name".Length;
//Get the index after the quotes
int end = nameSentence.LastIndexOf("out");
//Get the part of the string with its quotes
string name = nameSentence.Substring(begin, end - begin);
//Remove its quotes
string newName = name.Replace("\"", "");
//Replace new name (without quotes) within original sentence
string updatedNameSentence = nameSentence.Replace(name, newName);
//Returns "Take my name Wesley out of quotes"
return updatedNameSentence;

s = s.Replace( """", "" )
Two quotes next to each other will function as the intended " character when inside a string.

if you would like to remove a single character i guess it's easier to simply read the arrays and skip that char and return the array. I use it when custom parsing vcard's json.
as it's bad json with "quoted" text identifiers.
Add the below method to a class containing your extension methods.
public static string Remove(this string text, char character)
{
var sb = new StringBuilder();
foreach (char c in text)
{
if (c != character)
sb.Append(c);
}
return sb.ToString();
}
you can then use this extension method:
var text= myString.Remove('"');