How to replace multiple white spaces with one whit

Question

Let's say I have a string such as:

"Hello     how are   you           doing?"

I would like a function that turns multiple spaces into one space.

So I would get:

"Hello how are you doing?"

I know I could use regex or call

string s = "Hello     how are   you           doing?".replace("  "," ");

But I would have to call it multiple times to make sure all sequential whitespaces are replaced with only one.

Is there already a built in method for this?

Answer 1

Using the test program that Jon Skeet posted, I tried to see if I could get a hand written loop to run faster.
I can beat NormalizeWithSplitAndJoin every time, but only beat NormalizeWithRegex with inputs of 1000, 5.

static string NormalizeWithLoop(string input)
{
    StringBuilder output = new StringBuilder(input.Length);

    char lastChar = '*';  // anything other then space 
    for (int i = 0; i < input.Length; i++)
    {
        char thisChar = input[i];
        if (!(lastChar == ' ' && thisChar == ' '))
            output.Append(thisChar);

        lastChar = thisChar;
    }

    return output.ToString();
}

I have not looked at the machine code the jitter produces, however I expect the problem is the time taken by the call to StringBuilder.Append() and to do much better would need the use of unsafe code.

So Regex.Replace() is very fast and hard to beat!!