Replace the string of special characters in C#

Question

My requirement is:

I have to replace some special characters like * ' " , _ & # ^ @ with string.Empty, and I have to replace blank spaces with -.

This is my code:

 Charseparated = Charseparated
    .Replace("*","")
    .Replace("'","")
    .Replace("&","")
    .Replace("@","") ...

For so many characters to replace I have to use as many as Replace's which I want to avoid.

Is there another efficient way to remove the special characters, but at the same time replace blank spaces with -?

Answer 1

I believe, best is to use a regular expression here as below

s/[*'",_&#^@]/ /g

You can use Regex class for this purpose

Regex reg = new Regex("[*'\",_&#^@]");
str1 = reg.Replace(str1, string.Empty);

Regex reg1 = new Regex("[ ]");
str1 = reg.Replace(str1, "-");

Answer 2

Use Regular Expression

Regex.Replace("Hello*Hello'Hello&Hello@Hello Hello", @"[^0-9A-Za-z ,]", "").Replace(" ", "-")

It will replace all special characters with string.Empty and Space with "-"

Answer 3

Regex.Replace(source_string, @"[^\w\d]", "_");

This will replace all non-alphabets and non-numbers with '_' in the given string (source_string).

Answer 4

Make a collection of changes to make and iterate over it:

var replacements = new []
                   { new { Old = "*", New = string.Empty }
                   // all your other replacements, removed for brevity
                   , new { Old = " ", New = "-" }
                   }

foreach (var r in replacements)
{
    Charseparated = Charseparated.Replace(r.Old, r.New);
}

Answer 5

You can try using LINQ:

  var source = "lala * lalala @ whowrotethis # ohcomeon &";

  var result = string.Concat(source.Select(c => c == ' ' 
     ? "-" 
     : "*'\",_&#^@".Contains(c) ? "" 
     : c.ToString()));

Answer 6

The LINQ and char[] way:

   string f = Filter("*WHAT/ #PO#PO");

It returns WHAT-POPO:

    private string Filter(string s)
    {
        var chars = new[] { '*', '/', '#' };
        var filteredChars = s.ToArray();
        return new string(filteredChars
                 .Where(ch => !chars.Contains(ch) )
                 .Select(ch => ch == ' ' ? '-' : ch).ToArray());
    }

Answer 7

string.Replace is horrible, horrible, horrible and should not be used by professional programmers in anywhere but the most trivial of tasks.

Strings are immutable. This means that every time you do a string.replace (or a myString = myString + "lalala" and so on) the system needs to do all the logistics (creation of new pointer, copying of content, garbage collection etc). BTW, Patrick's answer above does just this (but with better code readability).

If this has to be done only a few times, it's not a problem --and the code is immediately readable.

But as soon as you put this operation in a loop, you need to write it in another way. I would go for regex myself:

string inStr = "lala * lalala @ whowrotethis # ohcomeon &";
string outStr = Regex.Replace(inStr , "[*|@|*|&]", string.Empty);

Answer 8

Here is the most optimal and easy way to do that

    public void foo()
    {
        string input = "A sample input a*b#c@d";
        string unwanted = "*'\",_&#^@";
        List<char> unwantedChars = unwanted.ToList<char>();
        StringBuilder sb = new StringBuilder();

        input = input.Replace(' ', '-');
        foreach(char c in input)
        {
            if (!unwantedChars.Any(x => x == c))
                sb.Append(c);
        }
        string output = sb.ToString(); //A-sample-input-abcd
    }

Answer 9

The OP asked for an "efficient" way to replace strings.

In terms of performance using Regex isn't the best solution (in case of readability or handiness it may be...).

Instead, StringBuilder preforms quite better, which may become important if you deal with large data.

 StringBuilder sb = new StringBuilder(myString);
 foreach (string unwanted in collectionOfUnwantedStrings)
         {
             sb.Replace(unwanted, string.Empty);
         }

Answer 10

Use string.Split with the array of separator chars, and aggregate them back in 1 string. Replacing with string.Empty and " " with "-" must be done separately, though.

        var res = "23#$36^45&".Split(new[] {'#', '$', '^', '&'}, StringSplitOptions.RemoveEmptyEntries)
            .Aggregate((s, s1) => s + s1);
        // "233645"

Answer 11

You can use Regex like this.

string Charseparated = "test * -";

var replacements = new Dictionary<string, string>()
{
   {"*", string.Empty},
   {" ", "-"}
};

var reg = new Regex(String.Join("|", replacements.Keys.Select(k => Regex.Escape(k))));
var reg_replace = reg.Replace(Charseparated, m => replacements[m.Value]);

Answer 12

pass string with special characters. you got only string without special characters. Note - add your special characters in "replaceables" list.

protected string hasSpecialChar(string input)
        {
            string[] replaceables = new[] { @"\", "|", "!", "#", "$", "%", "&", "/", "=", "?", "»", "«", "@", "£", "§", "€", "{", "}", "^", ";", "'", "<", ">", ",", "`" };
            string rxString = string.Join("|", replaceables.Select(s => Regex.Escape(s)));
            return Regex.Replace(input, rxString, "-");
        }

Answer 13

String str = "Whatever???@@##$ is#$% in& here";
     
str = Regex.Replace(str,@"[^\w\d\s]","");

Answer 14

The same question was asked to me in an interview... i was given a string which was containing special characters and was asked to remove the special characters from the input string and reverse it then.

Here is the simple and efficient program:

public class Program
    {
        static void Main(string[] args)
        {
            string name = "T@T@P&!M#";

            Program obj = new Program();

            Console.WriteLine(obj.removeSpecialCharacters(name));

            Console.WriteLine(obj.reverseString(obj.removeSpecialCharacters(name)));

            Console.ReadLine();


        }

        private string removeSpecialCharacters(string input)
        {
            string[] specialCharacters = new string[] { "@", "&", "!", "#" };

            for (int i = 0; i < specialCharacters.Length; i++)
            {
                if (input.Contains(specialCharacters[i]))
                {
                    input = input.Replace(specialCharacters[i], "");
                }
            }

            return input;
        }

        private string reverseString(string input)
        {
            string reverseString = "";

            for (int i = input.Length - 1; i >= 0; i--)
            {
                reverseString = reverseString + input[i];
            }

            return reverseString;
        }
    }