How do I replace multiple spaces with a single space in C#?

Question

How can I replace multiple spaces in a string with only one space in C#?

Example:

1 2 3  4    5

would be:

1 2 3 4 5         


        

Answer 1

Use the regex pattern

    [ ]+    #only space

   var text = Regex.Replace(inputString, @"[ ]+", " ");

Answer 2

For those, who don't like Regex, here is a method that uses the StringBuilder:

    public static string FilterWhiteSpaces(string input)
    {
        if (input == null)
            return string.Empty;

        StringBuilder stringBuilder = new StringBuilder(input.Length);
        for (int i = 0; i < input.Length; i++)
        {
            char c = input[i];
            if (i == 0 || c != ' ' || (c == ' ' && input[i - 1] != ' '))
                stringBuilder.Append(c);
        }
        return stringBuilder.ToString();
    }

In my tests, this method was 16 times faster on average with a very large set of small-to-medium sized strings, compared to a static compiled Regex. Compared to a non-compiled or non-static Regex, this should be even faster.

Keep in mind, that it does not remove leading or trailing spaces, only multiple occurrences of such.

Answer 3

Here is a slight modification on Nolonar original answer.

Checking if the character is not just a space, but any whitespace, use this:

It will replace any multiple whitespace character with a single space.

public static string FilterWhiteSpaces(string input)
{
    if (input == null)
        return string.Empty;

    var stringBuilder = new StringBuilder(input.Length);
    for (int i = 0; i < input.Length; i++)
    {
        char c = input[i];
        if (i == 0 || !char.IsWhiteSpace(c) || (char.IsWhiteSpace(c) && 
            !char.IsWhiteSpace(strValue[i - 1])))
            stringBuilder.Append(c);
    }
    return stringBuilder.ToString();
}

Answer 4

myString = Regex.Replace(myString, " {2,}", " ");

Answer 5

I know this is pretty old, but ran across this while trying to accomplish almost the same thing. Found this solution in RegEx Buddy. This pattern will replace all double spaces with single spaces and also trim leading and trailing spaces.

pattern: (?m:^ +| +$|( ){2,})
replacement: $1

Its a little difficult to read since we're dealing with empty space, so here it is again with the "spaces" replaced with a "_".

pattern: (?m:^_+|_+$|(_){2,})  <-- don't use this, just for illustration.

The "(?m:" construct enables the "multi-line" option. I generally like to include whatever options I can within the pattern itself so it is more self contained.

Answer 6

try this method

private string removeNestedWhitespaces(char[] st)
{
    StringBuilder sb = new StringBuilder();
    int indx = 0, length = st.Length;
    while (indx < length)
    {
        sb.Append(st[indx]);
        indx++;
        while (indx < length && st[indx] == ' ')
            indx++;
        if(sb.Length > 1  && sb[0] != ' ')
            sb.Append(' ');
    }
    return sb.ToString();
}

use it like this:

string test = removeNestedWhitespaces("1 2 3  4    5".toCharArray());