When I receive input via C# it comes in escaping the \. When I'm trying to parse the string it causes an error because its using \\r instead of \r in the string. Is there some way to prevent it from escaping the \ or perhaps turning \\ into \ in the string. I've tried:
protected string UnEscape(string s)
{
if (s == "")
return " ";
return s.Replace(#"\\", #"\");
}
With no luck. So any other suggestions.
EDIT:
I was not specific enough as some of you seemed confused as to what I'm trying to achieve. In debug I was reading "\\t" in a string but I wanted "\t" not because I want to output \t but because I want to output a [tab]. With the code above I was sort of trying to recreate something that has already been done through Regex.Unescape(string).
The problem is that most .NET components do not process backslash escape sequences in strings: the compiler does it for them when the string is presented as a literal. However, there is another .NET component that processes escape sequences - the regex engine. You can use Regex.Unescape to do unescaping for you:
string escaped = #"Hello\thello\nWorld!";
string res = Regex.Unescape(escaped);
Console.WriteLine(res);
This prints
Hello hello
World!
Note that the example uses a verbatim string, so \t and \n are not replaced by the compiler. The string escaped is presented to regex engine with single slashes, (although you would see double slashes if you look at the string in the debugger).
The problem is not that it's escaping the backslash, it's that it's not parsing escape sequences into characters. Instead of getting the \r character when the characters \\ and r are entered, you get them as the two separate characters.
You can't turn #"\\" into #"\" in the string, because there isn't any double backslashes, that's only how the string is displayed when you look at it using debugging tools. It's actually a single backslash, and you can't turn that into the \ part of an escape sequence, because that's not a character by itself.
You need to replace any escape sequence in the input that you want to convert with the corresponding character:
s = s.Replace("\\r", "\r");
Edit:
To handle the special case that Servy is talking about, you replace all escape sequences at once. Example:
s = Regex.Replace(s, #"\\([\\rntb])", m => {
switch (m.Groups[1].Value) {
case "r": return "\r";
case "n": return "\n";
case "t": return "\t";
case "b": return "\b";
default: return "\\";
}
});
If you have the three characters \, \, r in the input and you want to change this to the \r character then try
input.replace(#"\\r", "\r");
If you have the two characters \, r in the input and you want to change this to the \r character then try
input.replace(#"\r", "\r");
Related
I am trying to grab a handle to a file that has unicode characters in the filename.
For example, I have a file called c:\testø.txt. If I try new FileInfo("c:\testø.txt") I get an Illegal characters exception.
Trying again with an escape sequence: new FileInfo("c:\test\u00f8.txt") and it works! Yay!
So I've got a method to escape non-ASCII characters:
static string EscapeNonAsciiCharacters(string value)
{
StringBuilder sb = new StringBuilder();
foreach (char c in value)
{
if (c > 127)
{
// This character is too big for ASCII
string encodedValue = "\\u" + ((int)c).ToString("x4");
sb.Append(encodedValue);
}
else
{
sb.Append(c);
}
}
return sb.ToString();
}
But when I take the output from this method the escape characters seem to be incorrect.
EscapeNonAsciiCharacters("c:\testø.txt") ## => "c:\test\\u00f8.txt"
When I pass that output to the FileInfo constructor, I get the illegal chars exception again. However, the \ in c:\ seems to be unaltered. When I look at how this character is represented within the StringBuilder in the static method, I see: {c: est\u00f8.txt} which leads me to believe that the first backslash is being escaped differently.
How can I properly append the characters escaped by the loop in EscapeNonAsciiCharacters so I don't get the double escape character in my output?
You have more escaped in those strings than you probably intend.
Note that \ needs to be escaped when in a string, because it is itself the escape character and \t means tab.
Windows, using NTFS, is fully unicode-capable, so the original error is most likely due to you not escaping the \ character.
I wrote a toy application to deal with the file named ʚ.txt, and the constructor has no problem with that or any other unicode characters.
So, instead of writing new FileInfo("c:\testø.txt"), You need to write new FileInfo("c:\\testø.txt") or new FileInfo(#"c:\testø.txt").
Your escape function is entirely unnecessary in the context of C# in general and NTFS (or, really, most modern file systems). External libraries may, themselves, have incompatibilities with unicode, but that will need to be dealt with separately.
You seem to be misunderstanding escaped characters.
In this C# code, it is the compiler that converts the \u00f8 to the correct unicode character:
new FileInfo("c:\test\u00f8.txt") // (the "\t" is actually causing an error here)
What you are doing here is just setting encodedValue to the string "\u00f8", and there is nothing ever converting the escaped string to the converted string:
string encodedValue = "\\u" + ((int)c).ToString("x4");
If you want to convert the escaped string, then you need to do something like this:
How to convert a string containing escape characters to a string
I stuck in escape sequence in program.
I am getting input from xml file in single quotes.
So in string it may contain any escape sequence.
So what I want to do is consider next character after escape character as normal character.
Example: '\abc\\t'
Output: 'abc\t'
So for that I created regular expression which is:
Regex.Replace(SearchString, #"\\?(?<Character>)", "${Character}");
But it replaces all escape character and gives output :
abct
Please help me how can I do it?
The named group in your regular expression matches nothing, so it does the same as Replace(#"\", "").
Match one character in the group:
SearchString = Regex.Replace(SearchString, #"\\(.)", "$1");
Basically, you need parse your string character by character. Pseudo-code:
Loop through all characters c:
If c is escape character:
Read next character and do something special (\t is tab, \\ is backslash, ...)
Else:
Copy character to output
Try this:
Regex.Replace(SearchString, #"\\(?<Character>[^\\])", "${Character}");
What if you do like:
SearchString = SearchString.Replace(#"\\", #"\");
It would give:
\abc\t
Here escaped \t is now treated as a "tab character".
It is what you are looking for ?
I have stringBuilder & string class, storing a path:
StringBuilder name = new StringBuilder();
name.Append(#"NETWORK\MyComputer");
String serverName = name.ToString(); //this converts the \ to a \\
I have tried a number of things, but it always results in the string having \
Using serverName.Replace("\\", #"\"); doesn't work, it leaves it as a \
servername.Replace("\\", "\""); adds a " to the string, which is still not correct.
Please assist.
If you are concerned at a single back slash being shown as a double back slash then don't be - that is simply the way it is shown to you in the debugger.
The back slash is a special character, that 'specialness' is turned off by doubling it up. Alternatively the # symbol can be prefixed to the string in source code which avoids having to use it.
Use
name.Append(Path.Combine("NETWORK", "MyComputer");
In strings \ is an escape sequence. So \ in debugger will be \\
Acc.to MSDN
Character combinations consisting of a backslash (\) followed by a letter or by a combination of digits are called "escape sequences." To represent a newline character, single quotation mark, or certain other characters in a character constant, you must use escape sequences. An escape sequence is regarded as a single character and is therefore valid as a character constant.
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 ("). The following table lists the ANSI escape sequences and what they represent.
Read Escape Sequences
I don't think your code can be compiled. Because \ is an escape character, thus the string "\" will be wrong. The #"\" is right because the # (literal) has ignored that escape and tread it as a normal character.
See more here
I have a short question.
I want do put this \tssr>"&\8=f23' into a String (Language C#).
But the compiler always shows an error because for example "\8" is a command.
can someone help me?
Thank you very mutch.
string s = "\\tssr>\"&\\8=f23'";
OR
string s = #"\tssr>""&\8=f23'";
try
string s = #"\tssr>\"&\8=f23";
For double quote[EDIT]
string s = #"\tssr>""&\8=f23";
because \ is special char you need to escape it with either # for \\ as given in below answer
Just write \\8 instead of \8. Or put an # in front of the string. Other characters also need to be escaped with the \ character:
"\\tssr>\"&\\8=f23'"
or this:
#"\tssr>""&\8=f23'"
the backslash \ is used for escaping special characters, like tab or newline. Because of that, the first character also needs to be escaped, because \t is the escape code for Tab.
Try escape sequence
Check this
\\tssr>\"&\\8=f23\'
See below.
var str = "\\tssr>\"&\\8=f23'";
I add a backslash to escape the special characters
The backslash is an escape character in C#, which forms part of an escape sequence.
You have two options: either use TWO backslashes (also known as escaping the backslash) for example var foo = "hello\\world";, or embed the sequence into a string literal eg var foo = #"hello\world";.
Try this:
string s = " \\tssr>\"&\\8=f23' ";
simpleSound = new SoundPlayer(#"c:\Windows\Media\chimes.wav");
Why and what is the # for?
It's a literal string. Instead of having to escape the "\" by putting two of them "\" the compiler interprets the string "as is".
Say you wanted to print out the following text to the screen: "Hello \t world".
If you were to just do Console.WriteLine("Hello \t world"), then your output would be:
Hello world
notice the tab. That's because \t is interperted as a tab. If you use the literal though, like this:
Console.WriteLine(#"Hello \t world")
then your output would be:
"Hello \t world"
The # sign before a string means to treat the backslash as a normal character rather than the start of a special character (such as newline).
It identifies a string literal. It allows you to have the special character \ in the string without escaping it.
It is a verbatim string. A verbatim string allows you to include special characters like \, " etc. without using the escape sequence.
Another usage of # is that you can put it in front of a keyword, if you want to use a keyword as a variable name (even if it's not a good idea). Example:
public int #object = 1;
Defining the # symbol prior to the assigning a string value will prevent the need for doubling the backslash (\) in C#. The at symbol (#) simply ignores escape characters.
"c:\\my\\file.txt" could be done as #"c:\my\file.txt"
This means your \n and \t or whatever it is will also not be processed.