Fastest way to remove white spaces in string

Question

I'm trying to fetch multiple email addresses seperated by "," within string from database table, but it's also returning me whitespaces, and I want to remove the whitespace quickly.

The following code does remove whitespace, but it also becomes slow whenever I try to fetch large number email addresses in a string like to 30000, and then try to remove whitespace between them. It takes more than four to five minutes to remove those spaces.

 Regex Spaces =
        new Regex(@"\s+", RegexOptions.Compiled);
txtEmailID.Text = MultipleSpaces.Replace(emailaddress),"");

Could anyone please tell me how can I remove the whitespace within a second even for large number of email address?

Answer 1

I would build a custom extension method using StringBuilder, like:

public static string ExceptChars(this string str, IEnumerable<char> toExclude)
{
    StringBuilder sb = new StringBuilder(str.Length);
    for (int i = 0; i < str.Length; i++)
    {
        char c = str[i];
        if (!toExclude.Contains(c))
            sb.Append(c);
    }
    return sb.ToString();
}

Usage:

var str = s.ExceptChars(new[] { ' ', '\t', '\n', '\r' });

or to be even faster:

var str = s.ExceptChars(new HashSet<char>(new[] { ' ', '\t', '\n', '\r' }));

With the hashset version, a string of 11 millions of chars takes less than 700 ms (and I'm in debug mode)

EDIT :

Previous code is generic and allows to exclude any char, but if you want to remove just blanks in the fastest possible way you can use:

public static string ExceptBlanks(this string str)
{
    StringBuilder sb = new StringBuilder(str.Length);
    for (int i = 0; i < str.Length; i++)
    {
        char c = str[i];
        switch (c)
        {
            case '\r':
            case '\n':
            case '\t':
            case ' ':
                continue;
            default:
                sb.Append(c);
                break;
        }
    }
    return sb.ToString();
}

EDIT 2 :

as correctly pointed out in the comments, the correct way to remove all the blanks is using char.IsWhiteSpace method :

public static string ExceptBlanks(this string str)
{
    StringBuilder sb = new StringBuilder(str.Length);
    for (int i = 0; i < str.Length; i++)
    {
        char c = str[i];
        if(!char.IsWhiteSpace(c))
            sb.Append(c);
    }
    return sb.ToString();
}

Answer 2

Given the implementation of string.Replaceis written in C++ and part of the CLR runtime I'm willing to bet

email.Replace(" ","").Replace("\t","").Replace("\n","").Replace("\r","");

will be the fastest implementation. If you need every type of whitespace, you can supply the hex value the of unicode equivalent.

Answer 3

With linq you can do it simply:

emailaddress = new String(emailaddress
                                     .Where(x=>x!=' ' && x!='\r' && x!='\n')
                                     .ToArray());

I didn't compare it with stringbuilder approaches, but is much more faster than string based approaches. Because it does not create many copy of strings (string is immutable and using it directly causes to dramatically memory and speed problems), so it's not going to use very big memory and not going to slow down the speed (except one extra pass through the string at first).

Answer 4

emailaddress.Replace("  ", string.Empty);

Answer 5

You should try String.Trim(). It will trim all spaces from start to end of a string

Or you can try this method from linked topic: [link]

    public static unsafe string StripTabsAndNewlines(string s)
    {
        int len = s.Length;
        char* newChars = stackalloc char[len];
        char* currentChar = newChars;

        for (int i = 0; i < len; ++i)
        {
            char c = s[i];
            switch (c)
            {
                case '\r':
                case '\n':
                case '\t':
                    continue;
                default:
                    *currentChar++ = c;
                    break;
            }
        }
        return new string(newChars, 0, (int)(currentChar - newChars));
    }

Answer 6

You should consider replacing spaces on the record-set within your stored procedure or query using the REPLACE( ) function if possible & even better fix your DB records since a space in an email address is invalid anyways.

As mentioned by others you would need to profile the different approaches. If you are using Regex you should minimally make it a class-level static variable:

public static Regex MultipleSpaces = new Regex(@"\s+", RegexOptions.Compiled);

emailAddress.Where(x=>{ return x != ' ';}).ToString( ) is likely to have function overhead although it could be optimized to inline by Microsoft -- again profiling will give you the answer.

The most efficient method would be to allocate a buffer and copy character by character to a new buffer and skip the spaces as you do that. C# does support pointers so you could use unsafe code, allocate a raw buffer and use pointer arithmetic to copy just like in C and that is as fast as this can possibly be done. The REPLACE( ) in SQL will handle it like that for you.

Answer 7

Please use the TrimEnd() method of the String class. You can find a great example here.

Answer 8

There are many diffrent ways, some faster then others:

public static string StripTabsAndNewlines(this string str) {

    //string builder (fast)
    StringBuilder sb = new StringBuilder(str.Length);
    for (int i = 0; i < str.Length; i++) {
        if ( !  Char.IsWhiteSpace(s[i])) {
            sb.Append();
        }
    }
    return sb.tostring();

    //linq (faster ?)
    return new string(str.ToCharArray().Where(c => !Char.IsWhiteSpace(c)).ToArray());

    //regex (slow)
    return Regex.Replace(str, @"\s+", "")

}

Answer 9

string str = "Hi!! this is a bunch of text with spaces";

MessageBox.Show(new String(str.Where(c => c != ' ').ToArray()));

Answer 10

I haven't done performance testing on this, but it's simpler than most of the other answers.

var s1 = "\tstring \r with \t\t  \nwhitespace\r\n";
var s2 = string.Join("", s1.Split());

The result is

stringwithwhitespace

Answer 11

string input =Yourinputstring;
string[] strings = input.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
foreach (string value in strings)
{
   string newv= value.Trim();
   if (newv.Length > 0)
   newline += value + "\r\n";
}

Answer 12

string s = " Your Text ";

string new = s.Replace(" ", string.empty);

// Output:
// "YourText"

Answer 13

Fastest and general way to do this (line terminators, tabs will be processed as well). Regex powerful facilities don't really needed to solve this problem, but Regex can decrease performance.

new string
    (stringToRemoveWhiteSpaces
       .Where
       (
         c => !char.IsWhiteSpace(c)
       )
       .ToArray<char>()
    )