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 whitesp

Answer 1

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

public static string ExceptChars(this string str, IEnumerable 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(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();
}