I have a simple line of code in a web service:
instance = #"\instanceNameHere";
Yet the output is always the same.
\\instanceNameHere
If I remove the # and use two slashes, I get the same result. I've never seen this before and my Google-fu has failed me. I even wrote a simple app and the result was correct. So why is it acting up in the web service?
It's escaping the slash for you in the debugger so you know that it's a slash and not an escape sequence like \t. If the debugger did not do this, how could you distinguish the string
\t
from the string
<tab>
in the debugger since the latter is represented in an escape sequence by \t? Therefor the former is shown as
\\t
and the latter as
\t
Write it to a stream or the console and you'll see that it only has one slash, or do instance.Length and compare to a count of the characters. You'll see 17 on the console, whereas \\instanceNameHere has eighteen characters.
The debugger displays strings as C# literals. So it's displaying them with characters escaped. It would also show carriage returns as \r and tabs as \t. This is purely for visualization -- the string does not literally contain these escape characters. If you write it out to a log, it will not include the escape characters -- it will look as you expect.
A UNC name of any format, which always start with two backslash characters ("\").
Link
Update : Please see #Jason post above! I didn't realise he was checking in the debugger.
Related
string pat12 = #"\e\[36m(.+)";
line2parse = "[36mA Rocky Landing";
if (Regex.Match(line2parse,pat12).Success)
{
Console.WriteLine("ROOM NAME: "+Regex.Match(line2parse,pat12).Groups[1].ToString().Trim());
}
NOTE: You are unable to see the ESC sequence before the [36 in my variable "line2parse" but its there. If I wanted to make it show up in Notepad++ I would hold down ALT and type "027" on the numpad. It then shows up as ESC in Notepad++. In C# console it shows up as a left pointing arrow. Ironically I can do "ALT + 27" and it shows that left arrow in Notepad++ (but if i add the 0, it does the ESC look instead of the arrow)
I am doing many Regex matches so the problem isn't with my Regex variable or anything like that. I cannot get this to match properly despite it working at this site: http://regexstorm.net/tester
At that site, this is the pattern: "\e[36m(.+)" (without quotes) and this is the input: [36mA Rocky Landing (again you can't see the escape thing). It then tells me $1 would be "A Rocky Landing" but in my actual code, it doesn't match.
What am I doing wrong?
I have looked through quite a few other, similar, posts and based on what they say, I believe this should work. I even tried [^\x00-\x7F] as my escape char catch and it still wont match.
Why do you think \e is the escape sequence for an escape character? You need to use \x1b instead.
string pat12 = #"\x1b\[36m(.+)";
I am reading a text file with this structure:
20150218;"C7";"B895";00101;"FTBCCAL16"
I read the line and split like this:
System.IO.StreamReader fichero = new System.IO.StreamReader(ruta, Encoding.Default);
while ((linea = fichero.ReadLine()) != null)
{
// Split by ";"
String[] separador = linea.Split(';');
}
But when I see the content of "linea", I have this:
"20150218";\"C7\";\"B895\";"00101";\"FTBCCAL16\"
As you see, the streamreader add some special character to the output like "" and \. I want to obtain this.
20150218;"C7";"B895";00101;"FTBCCAL16"
Is there a way to obtain this?
Thanks in advance! Regards!
You are watching it in Visual Studio debugger, which just shows you your lines this way. You can write your result into a console or into the file. And you will see normal text without special characters.
StreamReader is not adding or modifying the strings read from the file at all.
If you are viewing the contents of separador in the Visual Studio debugger, it will add an escape sequence to any special characters (for display purposes).
The displayed format matches how you would have to enter them in the code editor if you were creating a string constant.
For example,
However, the real contents of these strings (in memory) are not escaped. They are exactly as you expect them to be in your question.
If you output them or try to manipulate them in code they will have the correct contents.
So, your code is correct. You just have to understand escape sequences and how strings appear in the Visual Studio debugger.
Update:
See this question for an explanation of how to display unquoted strings in the debugger.
Okay here is the quotation from MSDN
At compile time, verbatim strings are converted to ordinary strings with all the same escape sequences. Therefore, if you view a verbatim string in the debugger watch window, you will see the escape characters that were added by the compiler, not the verbatim version from your source code. For example, the verbatim string #"C:\files.txt" will appear in the watch window as "C:\files.txt".
In your case for " it uses \" (Verbatim string)and this can be visible at debugging time.
Why this happens ?
Double quotation mark " is an escape sequence
Escape sequences are typically used to specify actions such as carriage returns and tab movements on terminals and printers. They are also used to provide literal representations of nonprinting characters and characters that usually have special meanings, such as the double quotation mark (")
So when a string purposefully contains an escape sequence, you need to represent it as a verbatim string. That's what compiler do and that's what you see in debugger
I need to replace all ocurrences of a dot with a backslash in C# with the string "\." (escape the dot),
Wath I've tried:
string.Replace(".", "\\.");
string.Replace(".", #"\.");
string.Replace(".", #"\\\.");
all my tries finish with an even number of backslashes before the dot, that are removed automatically after.
Thanks
The first two both work perfectly!
You're probably watching the values with the Watch function from a breakpoint, but this shows backslashes with additional escapes.
If you just output the string to something like the console or a file, you'll see that it works.
There is a method designed for this: Regex.Escape().
hi , I have 2 related questions.
1)suppose we have:
string strMessage="\nHellow\n\nWorld";
console.writeln(strMessage);
Result is:
Hellow
World
Now if we want to show the string in the original format in One Line
we must redefine the first variable from scratch.
string strOrignelMessage=#"\nHellow\n\nWorld" ;
console.writln(strOrignelMessage);
Result is:
\nHellow\n\nWorld --------------------->and everything is ok.
i am wondering is there a way to avoid definning
the new variable(strOrignelMessage) in code for this purpose and just using only
the first string variable(strMessage) and apply some tricks and print it in one line.
at first i tried the following workaround but it makes some bugs.suppose we have:
string strMessage="a\aa\nbb\nc\rccc";
string strOrigenalMessage=strMessage.replace("\n","\\n").replace("\r","\\r");
Console.writeln(strOrigenalMessage)
result is :aa\nbb\nc\rccc
notice that befor the first "\" not printed.and now my second question is:
2)How we can fix the new problem with single "\"in the string
i hope to entitle this issue correctly and my explanations would be enough,thanks
No, because the compiler has already converted all of your escaped characters in the original string to the characters they represent. After the fact, it is too late to convert them to non-special characters. You can do a search and replace, converting '\n' to literally #"\n", but that is whacky and you're better off defining the string correctly in the first place. If you wanted to escape the backslashes in the first place, why not put an extra backslash character in front of each of them:
Instead of "\n" use "\\n".
Updated in response to your comment:
If the string is coming from user input, you don't need to escape the backslash, because it will be stored as a backslash in the input string. The escape character only works as an escape character in string literals in code (and not preceded by #, which makes them verbatim string literals).
if you want "\n\n\a\a\r\blah" to print as \n\n\a\a\r\blah without # just replace all \ with \\
\ is the escaper in a non-verbatim string. So you simply need to escape the escaper, as it were.
If you want to use both strings, but want to have only one in the code then write the string with #, and construct the other one with Replace(#"\n","\n").
explanations for Anthony Pegram (if i understand u right) and anyone that found it usefull
i think i find my way in question2.
at first ,unfortunately,i thought that the
escape characters limts to \n,\t,\r,\v and
this made me confuesed becouse in my sample string i used \a and \b
and the compiler behaviuor was not understandable for me.
but finally i found that \a and \b is in
escape-characters set too.and if u use "\" without escap characters
a compile time error would be raised (its so funny when i think to My mistake again)
pls refers to this usefull msdn article for more info.
2.4.4.5 String literals
and you couldnt replace \ (single\) with \\
becouse fundamentally you couldnt have a (single \) without using
escape-characters after it in a string .so we coudnt write such a string in the code:
string strTest="abc\pwww"; ------> compile time error
and for retriving an inactived escape characters version of a string
we can use simply string.replace method as i used befor.
excuse me for long strory ,thank u all for cooperation.
"C://test/test/test.png" -> blub
blub = blub.Replace(#"/", #"\");
result = "C:\\\\test\\test\\test.png"
how does that make sense? It replaces a single / with two \
?
It's actually working:
string blub = "C://test/test/test.png";
string blub2 = blub.Replace(#"/", #"\");
Console.WriteLine(blub);
Console.WriteLine(blub2);
Output:
C://test/test/test.png
C:\\test\test\test.png
BUT viewing the string in the debugger does show the effect you describe (and is how you would write the string literal in code without the #).
I've noticed this before but never found out why the debugger chooses this formatting.
No, it doesn't.
What you're seeing is the properly formatted string according to C# rules, and since the output you're seeing is shown as though you haven't prefixed it with the # character, every backslash is doubled up, because that's what you would have to write if you wanted that string in the first place.
Create a new console app and write the result to the console, and you'll see that the string looks like you wanted it to.
So this is just an artifact of how you look at the string (I assume the debugger).
The \ character in C# is the escape character, so if you are going to use it as a \ character you need two - otherwise the next character gets treated specially (new line etc).
See What character escape sequences are available? (C#)
The character \ is a special character, which changes the meaning of the character after it in string literals. So when you refer to \ itself, it needs to be escaped: \\.
Look up "escape characters".
Its done what it should.
"\\" is the same as #"\"
"\" is an escape character. Without the verbatim indicator "#" before a string a single \ is shown as "\\"
You should think twice before saying something like that....
The string.Replace function is basic functionality that has been around for a long time.... Whenever you find you have a problem with something like that, it's probably not the function that is broken, but your understanding or use of it.