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How to unescape multibyte unicode in c# [duplicate]

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How to unescape unicode string in C#
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Closed 2 years ago.
The following unicode string from a text file encodes a single apostrophe using 3 bytes:
It\u00e2\u0080\u0099s working
This should decode to:
It’s working
How can I decode this string in C#?
For example, when I try the following code:
string test = #"It\u00e2\u0080\u0099s working";
string test2 = System.Text.RegularExpressions.Regex.Unescape(test);
it incorrectly decodes the first byte only:
Itâ\u0080\u0099s awesome

This is UTF8. Try UTF8 Encoding
using System.Text;
using System.Text.RegularExpressions;
string test = "It\u00e2\u0080\u0099s working";
byte[] bytes = Encoding.GetEncoding(28591)
.GetBytes(test);
var converted = Encoding.UTF8.GetString(bytes);//It’s working

try this to parse file :
private static Regex _regex = new Regex(#"\\u(?<Value>[a-zA-Z0-9]{4})", RegexOptions.Compiled);
public string decodeString(string value)
{
return _regex.Replace(
value,
m => ((char)int.Parse(m.Groups["Value"].Value, NumberStyles.HexNumber)).ToString()
);
}

That is javascript unicode encoding. Use a C# javascript deserializer to convert it.
(I don't have enough reputation to comment, so I will write here)
Where did you get those characters from in the first place?
\uXXXX is an encoding used by JavaScript and C# (didn't know about C# this until now) to encode 16 bit Unicode characters in string literals. 16 bit - 4 hex characters, so \uXXXX, each X representing one Hexadecimal digit.
Note this is used to encode string literals in source code! It is not used to encode the bytes stored in files or memory or what not. It is an older style of encoding due to modern source code editors usually support UTF-8 or UTF-16 or some other encoding to be able to store unicode characters in source code files, and then they are also able to display the unicode character symbol, and allow it being typed right at the editor. So \uXXXX typing is not needed, and going out of style.
So that is why I asked where did you get the string initially? You wrote in one comment you read it from a file? What generated the file?
If each \uXXXX is taken alone by itself as unicode characters, which is what \uXXXX means, doesn't make sense being there. 00e2 is a character a with cap on it, 0080 and 0099 are control characters, not printable.
If e28099 are taken together as three single bytes, i.e. dropping off 00 valued first bytes of each as they are in the form of \u00XX then it fits as a UTF8 character representation of a Unicode character with decimal value 2019, which is "Unicode Character 'RIGHT SINGLE QUOTATION MARK' (U+2019)"
Then that is what you are looking for, but this doesn't seem correct usage of encoding that generated that string. If you end up with those strings and have to evaluate them, then comments above by "C# Novice" is working, but it may not work in every case.
You could convert string literals that uses \uXXXX encoding in its strings using a javascript script evaluator, or CSharpScript.Run() to make a string literal with those and assign to a variable, and then look at its bytes. But I tried that later and due to those byte values/characters not making sense I don't get anything meaningful from them. I get an a with a cap, and the next two, CSharpScript refuses to decode and leaves as is. Becuase those are control characters when decoded.
Here three different ways using C# avaliable libraries doing \uXXXX decoding. The first two uses NewtonSoft.JSON package, the last uses Roslyn/CSharpScript, both avalilable from Nuget. Note none of these print single aposthrope, due to what I described above. In contrast, if I change the string to "\u3053\u3093\u306B\u3061\u306F\u4E16\u754C!", it prints on the debug output window this Japanese text: "こんにちは世界!" , which is what Google translate told me is Japanese translation of "Hello World!"
https://translate.google.com/?sl=ja&tl=en&text=%E3%81%93%E3%82%93%E3%81%AB%E3%81%A1%E3%81%AF%E4%B8%96%E7%95%8C!&op=translate
So in summary, whatever generated those scripts, doesn't seem to be doing standard things.
string test = #"It\u00e2\u0080\u0099s working";
// Using JSON deserialization, since \uXXXX is valid encoding JavaScript string literals
// Have to add starting and ending quotes to make it a script literal definition, then deserialize as string
var d = Newtonsoft.Json.JsonConvert.DeserializeObject("\"" + test + "\"", typeof(string));
Console.WriteLine(d);
System.Diagnostics.Debug.WriteLine(d);
// Another way of JavaScript deserialization. If you are using a stream like reading from file this maybe better:
TextReader reader = new StringReader("\"" + test + "\"");
Newtonsoft.Json.JsonTextReader rdr = new JsonTextReader(reader);
rdr.Read();
Console.WriteLine(rdr.Value);
System.Diagnostics.Debug.WriteLine(rdr.Value);
// lastly overkill and too heavy: Using Roslyn CSharpScript, and letting C# compiler to decode \uXXXX's in string literal:
ScriptOptions opt = ScriptOptions.Default;
//opt = opt.WithFileEncoding(Encoding.Unicode);
Task<ScriptState<string>> task = Task.Run(async () => { return CSharpScript.RunAsync<string>("string str = \"" + test + "\".ToString();", opt); }).Result;
ScriptState<string> s = task.Result;
var ddd = s.Variables[0];
Console.WriteLine(ddd.Value);
System.Diagnostics.Debug.WriteLine(ddd.Value);

when i decrypt base64 string in c# it shows me ????? question mark and some special character sign

i have a base64 string and i want to decrypt it thru c# code. but when i apply below code, it shows me question mark and differnt special characters.
i dont know why it is showing this.
byte[] data = Convert.FromBase64String(encpStr);
string decodedString = Encoding.UTF8.GetString(data);
i created console project in visual studio, and doing this practice. see my whole code below.
string encStr = "oJe6iooq+PbvArD+C7P7B/cHAAL9Dr2/vvIBFRcVCAYfxxEcygzMFB0eFNEWFC3VKibYLCknMiLeLzU7PC8pOPT19g==";
Console.WriteLine("******************\nEnc String:\n" + encStr + "\n\n\n**********************");
byte[] data = Convert.FromBase64String(encStr);
string decStr = Encoding.UTF8.GetString(data);
Console.WriteLine("\n\n\nDecr String: \n" + decStr + "\n\n");
Console.ReadKey();

By default many systems/languages display byte values that can not be represented as a ?, � or similar glyph.
Base64 is encoding not encryption.
Base64 encoding is generally used when data needs to be handled as a character string but the data values are not representable as characters (or at least not all).
Data is generally a collection of 8-bit bytes such as in an array. Eamples include images, compiled computer code, encrypted data and etc.
Not all, even most, byte values do not have a character representation and do not have a displayable representation. See ASCII, unicode and in particular UTF-8 as well as Base64.

Base64 is used to encode binary data as text. If you decode Base64 data, you therefore get binary data. Most binary data cannot be represented as a string (or any other form of text) because it simply is not text.
Your Base64 is such an example. The result is not text, neither in UTF-8, nor in ASCII nor in any other encoding.
That's why you get a bunch on funny characters. They are used to represent invalid characters.

Base64 encoded String that contains exclamation points causing exception

Unfortunately, I cannot post the string as it contains sensitive data. I have created an API that is in use at my company. We have a partner that is attempting to use said API. In a part of the JSON there we expect a base64 encoded string of a digitally signed XML file. When I parse the JSON and try to decode the Base64 string, the API throws an exception.
System.FormatException occurred HResult=0x80131537
Message=The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters.
Source=mscorlib
StackTrace:
at System.Convert.FromBase64_Decode(Char* startInputPtr, Int32 inputLength, Byte* startDestPtr, Int32 destLength)
at System.Convert.FromBase64CharPtr(Char* inputPtr, Int32 inputLength)
at System.Convert.FromBase64String(String s)
at Base64Decoding.Program.Main(String[] args) in
I have tried taking the raw XML and encoding it on 3 different machines, including a Linux system using Python, I have gotten the exact same Base64 string each time. The string that I receive does not match his string.
This is the only partner we work with that has ever had an issue with the encoding and not matter what I have tried, I cannot duplicate his results encoding the signed XML file. When I try to decode his Base64 using an online decoder, it displays an error. But when I click the decode button, it actually downloads the correctly decoded XML!
When I use my encoded string of the same file, it does not display the error, it displays the decoded XML in the 'live view' box and downloads the correct XML when I click the decode button.
Does anyone have any idea what might cause System.Convert.ToBase64String() to output a string with exclamation points in it? To my understanding that should not be an allowed character in Base64. I have tried 64 vs. 32 bit, I have tried every version of the .Net Framework to back to 2.

Try replacing every exclamation point character '!' with a forward slash character '/'.
I have seen base64 encoded data with exclamation marks in it before. Usually it was embedded in HTML or was intended to be embedded in HTML. Presumably, because forward slashes are a syntactically meaningful character in HTML, and because base64 encoded data can have forward slashes in it, all the forward slashes have been replaced by an exclamation point.
I've seen people who have embedded WebAssembly programs in javascript tags do this.
As an additional note, if you have a piece of base64 encoded data, especially one that might be truncated or only part of the full base64 encoded string, and the framework is giving you an exception like the one above or an exception that says "Invalid length for a Base-64 char array or string", you can try either removing characters from the end of the string, one-by-one, trying to decode it each time (up to about 4 characters or so--beyond that its probably not a length/padding problem), or by adding padding characters '=' (equals symbol) one-by-one, but not more than twice (for a total of two equals, ie '==').

Can't decode a base 64 string with Convert.FromBase64String()

I'm using Convert.FromBase64String() for decoding a base 64 encoded string. The string actually is a XML file, which has base 64 encoded images in it. E.g.
data:image/png;base64,iVBORw0KGgoAA...
I get the following exception:
System.FormatException: The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters.
Where is the problem? The double base 64 encoding? The string image/png;base64 in the base 64 encoded data? An online tool has no issues at all.
Edit:
Now I tried to remove image/png;base64 part from the XML file and I still get this error. Then I tried to decode the string YWJj with the same error!? If I use this code
byte[] dataBuffer = Convert.FromBase64String(base64string);
I get the above exception. If I use instead
byte[] dataBuffer = Convert.FromBase64String("YWJj");
it does work. Encoding of the file is UTF-8 according to Notepad++. Any ideas?
Edit 2:
String.Equals says that the two strings YWJj are not equal, despite the Locals Window shows that they are:
BTW the above code doesn't throw the exception, because I use string test = "YWJj";. Why does it work with local defined variables, but not with passed strings? I don't think it's a threading problem, because I made the above function, which is only called once.

You should remove data:image/png;base64, part from string to decode.
strind data = "data:image/png;base64,iVBORw0KGgoAA...";
string[] pd = data.Split(',');
string decoded = Convert.FromBase64String(pd[1]);
The part of string data:image/png;base64, isn't base64 data. Real encoded data starts after ,. Base64 description. So function Convert.FromBase64String accepts only encoded data. Therefore, you need to extract the encoded data.

As I've already written I'm reading the base 64 encoded file in and decode it with Convert.FromBase64String(). Now I got it working and the reason is completely unknowable. What I've done?
I renamed the file. That's it.
Before I had a filename like NAME_Something_v1.0.xsl.b64. Now I use NAME_Something.b64. Perhaps it's not the only reason, but I'm accessing the file from an assembly with assembly.GetManifestResourceStream(). I've cleaned the solution before, but I always had the same problem. Now I changed the name back to where it was and it also works ...

1. You shouldn't include the data:image/png;base64, part, as this isn't actually a part of the base64 string.
2. iVBORw0KGgoAA... isn't valid either, this is not the full base64 string.
You can solve this by either splitting the string or using regular expressions to parse it.

Everything after data:image/png;base64, is the actual Base64 string to be decoded.
You can remove the first part of the string like so:
ImageAsString = ImageAsString.Substring(input.IndexOf('data:image/png;base64,') + 1);

Base64 String throwing invalid character error

I keep getting a Base64 invalid character error even though I shouldn't.
The program takes an XML file and exports it to a document. If the user wants, it will compress the file as well. The compression works fine and returns a Base64 String which is encoded into UTF-8 and written to a file.
When its time to reload the document into the program I have to check whether its compressed or not, the code is simply:
byte[] gzBuffer = System.Convert.FromBase64String(text);
return "1F-8B-08" == BitConverter.ToString(new List<Byte>(gzBuffer).GetRange(4, 3).ToArray());
It checks the beginning of the string to see if it has GZips code in it.
Now the thing is, all my tests work. I take a string, compress it, decompress it, and compare it to the original. The problem is when I get the string returned from an ADO Recordset. The string is exactly what was written to the file (with the addition of a "\0" at the end, but I don't think that even does anything, even trimmed off it still throws). I even copy and pasted the entire string into a test method and compress/decompress that. Works fine.
The tests will pass but the code will fail using the exact same string? The only difference is instead of just declaring a regular string and passing it in I'm getting one returned from a recordset.
Any ideas on what am I doing wrong?

You say
The string is exactly what was written
to the file (with the addition of a
"\0" at the end, but I don't think
that even does anything).
In fact, it does do something (it causes your code to throw a FormatException:"Invalid character in a Base-64 string") because the Convert.FromBase64String does not consider "\0" to be a valid Base64 character.
byte[] data1 = Convert.FromBase64String("AAAA\0"); // Throws exception
byte[] data2 = Convert.FromBase64String("AAAA"); // Works
Solution: Get rid of the zero termination. (Maybe call .Trim("\0"))
Notes:
The MSDN docs for Convert.FromBase64String say it will throw a FormatException when
The length of s, ignoring white space
characters, is not zero or a multiple
of 4.
-or-
The format of s is invalid. s contains a non-base 64 character, more
than two padding characters, or a
non-white space character among the
padding characters.
and that
The base 64 digits in ascending order
from zero are the uppercase characters
'A' to 'Z', lowercase characters 'a'
to 'z', numerals '0' to '9', and the
symbols '+' and '/'.

Whether null char is allowed or not really depends on base64 codec in question.
Given vagueness of Base64 standard (there is no authoritative exact specification), many implementations would just ignore it as white space. And then others can flag it as a problem. And buggiest ones wouldn't notice and would happily try decoding it... :-/
But it sounds c# implementation does not like it (which is one valid approach) so if removing it helps, that should be done.
One minor additional comment: UTF-8 is not a requirement, ISO-8859-x aka Latin-x, and 7-bit Ascii would work as well. This because Base64 was specifically designed to only use 7-bit subset which works with all 7-bit ascii compatible encodings.

string stringToDecrypt = HttpContext.Current.Request.QueryString.ToString()
//change to
string stringToDecrypt = HttpUtility.UrlDecode(HttpContext.Current.Request.QueryString.ToString())

If removing \0 from the end of string is impossible, you can add your own character for each string you encode, and remove it on decode.

One gotcha to do with converting Base64 from a string is that some conversion functions use the preceding "data:image/jpg;base64," and others only accept the actual data.