CODEWITHSUNDEEP
c#stringwinformsstring-formatting
regisls
regisls

Reputation: 529

Render special character C#

I have a string that has special characters like this example: 12345678912\rJ\u0011 because I need to have access to this special chars to configure my application. I want to display this string exactly like this in a TextBox field so everything I have tried so far results in a string where the character \u0011 tries to render with an empty character at the end: "7896104866061\rJ".

I made this but it doesn't work.

string result = Regex.Replace(
    ToLiteral(this.Buffer), 
   "[^\x00-\x7Fd]", 
    c => string.Format("\\u{0:x4}", (int)c.Value[0]))
 .Replace(@"\", @"\\");

public static string ToLiteral(string input)
    {
        using (var writer = new StringWriter())
        {
            using (var provider = CodeDomProvider.CreateProvider("CSharp"))
            {
                provider.GenerateCodeFromExpression(
                    new CodePrimitiveExpression(input), 
                    writer, 
                    null);

                return writer.ToString();
            }
        }
    }

What need I do? Thanks in advance.

Upvotes: 6

Views: 2698

Answers (3)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186698

Let's build the string in a loop; we have several categories of characters:

  1. Known controls like \n, \t, \r
  2. Controls like \u0011
  3. Characters which should be escaped: " and \
  4. Plain charactes which should be put as they are

Code:

using System.Linq;
...

private static IReadOnlyDictionary<char, string> s_KnownControls = new 
  Dictionary<char, string>() {
    { '\0', "\\0"},
    { '\a', "\\a"},
    { '\b', "\\b"},
    { '\n', "\\n"},
    { '\v', "\\v"},
    { '\t', "\\t"},
    { '\f', "\\f"},
    { '\r', "\\r"},
  };

public static string ToLiteral(string input) {
  if (null == input)
    return null;

  StringBuilder sb = new StringBuilder();

  foreach (var c in input) {
    if (char.IsControl(c))
      sb.Append(s_KnownControls.TryGetValue(c, out var s) 
        ? s 
        : $"\\u{((int)c):x4}");
    else {
      if (c == '"' || c == '\\') // escapement 
        sb.Append('\\'); 

      sb.Append(c);
    } 
  }

  return sb.ToString();  
}

Demo:

  string[] tests = new string[] {
    "12345678912\rJ\u0011",
    "abc\tdef\t\0A\n\a\bB",
    "abc\"def\"xyz\\pqr"
  };

  string report = string.Join(Environment.NewLine, tests
    .Select(test => ToLiteral(test)));

Outcome:

12345678912\rJ\u0011
abc\tdef\t\0A\n\a\bB
abc\"def\"xyz\\pqr

Upvotes: 1

Fabio
Fabio

Reputation: 175

Here my snippet to display ctrl chars: https://gist.github.com/TheTrigger/6efa6a8e42eedf1e61e0db8e9ef4360a

using System.Text;

namespace CtrlCharReplace
{
    public static class Extensions
    {
        public static string ReplaceCtrl(this string s)
        {
            var sb = new StringBuilder();
            for (int i = 0; i < s.Length; i++)
            {
                char c = s[i];

                var isCtrl = char.IsControl(c);
                var n = char.ConvertToUtf32(s, i);

                if (isCtrl)
                {
                    sb.Append($"\\u{n:X4}");
                }
                else
                {
                    sb.Append(c);
                }
            }

            return sb.ToString();
        }
    }
}

Upvotes: 2

user11546311
user11546311

Reputation:

Do the replace of \ with \\ before the call to ToLiteral, and you will get the desired output.

string result = Regex.Replace(ToLiteral("12345678912\\rJ\\u0011".Replace(@"\", @"\\")), "[^\x00-\x7Fd]", c => string.Format("\\u{0:x4}", (int)c.Value[0]));

Upvotes: 1

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