转到字符串中的每个空白。 C＃

Question

Is it possible to pass over a string, finding the white spaces?

For example a data set of:

string myString = "aa bbb cccc dd";

How could I loop through and detect each white space, and manipulate that space?

I need to do this in the most effecient way possible.

Thanks.

UPDATE:
I need to manipulate the space by increasing the white space from an integer value. So for instance increase the space to have 3 white spaces instead of one. I'd like to make it go through each white space in one loop, any method of doing this already in .NET? By white space I mean a ' '.

Answer 1

You can use the Regex.Replace method. This will replace any group of white space character with a dash:

myString = Regex.Replace(myString, "(\s+)", m => "-");

Update:

This will find groups of space characters and replace with the tripple amount of spaces:

myString = Regex.Replace(
  myString,
  "( +)",
  m => new String(' ', m.Groups[1].Value.Length * 3)
);

However, that's a bit too simple to make use of regular expressions. You can do the same with a regular replace:

myString = myString.Replace(" ", "   ");

This will replace each space intead of replace groups of spaces, but the regular replace is much simpler than Regex.Replace , so it should still be at least as fast, and the code is simpler.

Answer 2

If you want to replace all whitespace in one swoop, you can do:

// changes all strings to dashes
myString.Replace(' ', '-');

If you want to go case by case (that is, not just a mass replace), you can loop through IndexOf() :

int pos = myString.IndexOf(' ');

while (pos >= 0)
{
    // do whatever you want with myString @ pos

    // find next
    pos = myString.IndexOf(' ', pos + 1);
}

UPDATE

As per your update, you could replace single spaces with the number of spaces specified by a variable (such as numSpaces ) as follows:

myString.Replace(" ", new String(' ', numSpaces));

Answer 3

Depending on what you're tring to do:

for(int k = 0; k < myString.Length; k++)
{
   if(myString[k].IsWhiteSpace())
   {
       // do something with it
   }
}

The above is a single pass through the string, so it's O(n). You can't really get more efficient that that.

However, if you want to manipulate the original string your best bet is to Use a StringBuilder to process the changes:

StringBuilder sb = new StringBuilder(myString);
for(int k = 0; k < myString.Length; k++)
{
   if(myString[k].IsWhiteSpace())
   {
       // do something with sb
   }
}

Finally, don't forget about Regular Expressions. It may not always be the most efficient method in terms of code run-time complexity but as far as efficiency of coding it may be a good trade-off.

For instance, here's a way to match all white spaces:

var rex = new System.Text.RegularExpressions.Regex("[^\\s](\\s+)[^\\s]");
var m = rex.Match(myString);
while(m.Success)
{
    // process the match here..

    m.NextMatch();
}

And here's a way to replace all white spaces with an arbitrary string:

var rex = new System.Text.RegularExpressions.Regex("\\s+");
String replacement = "[white_space]";
// replaces all occurrences of white space with the string [white_space]
String result = rex.Replace(myString, replacement);

Answer 4

If you just want to replace all spaces with some other character:

myString = myString.Replace(' ', 'x');

If you need the possibility of doing something different to each:

foreach(char c in myString)
{
    if (c == ' ')
    {
        // do something
    }
}

Edit:

Per your comment clarifying your question:

To change each space to three spaces, you can do this:

myString = myString.Replace(" ", "   ");

However note that this doesn't take into account instances where your input string already has two or more spaces. If that is a possibility you will want to use a regex.

Answer 5

LINQ query below returns a set of anonymous type items with two properties - "sybmol" represents a white space character, and "index" - index in the input sequence. After that you have all whitespace characters and a position in the input sequence, now you can do what you want with this.

string myString = "aa bbb cccc dd";
var res = myString.Select((c, i) => new { symbol = c, index = i })
                  .Where(c => Char.IsWhiteSpace(c.symbol));

EDIT: For educational purposes below is implementation you are looking for, but obviously in real system use built in string constructor and String.Replace() as shown in other answers

string myString = "aa bbb cccc dd";
var result = this.GetCharacters(myString, 5);
string output = new string(result.ToArray());


public IEnumerable<char> GetCharacters(string input, int coeff)
{
    foreach (char c in input)
    {
        if (Char.IsWhiteSpace(c))
        {
            int counter = coeff;
            while (counter-- > 0)
            {
                yield return c;
            }
        }
        else
        {
            yield return c;
        }
    }
}

Answer 6

var result = new StringBuilder();

foreach(Char c in myString)
{
   if (Char.IsWhiteSpace(c))
   {
       // you can do what you wish here. strings are immutable, so you can only make a copy with the results you want... hence the "result" var.

      result.Append('_'); // for example, replace space with _
   }
   else result.Append(c);

}

myString = result.ToString();

Answer 7

If you want to replace the white space with, eg '_', you can using String.Replace .

Example:

string myString = "aa bbb cccc dd";
string newString = myString.Replace(" ", "_"); // gives aa_bbb_cccc_dd

Answer 8

使用string.Replace() 。

string newString = myString.Replace(" ", "   ");

Answer 9

In case you want to left/right justify your string

int N=10;
string newstring = String.Join(
        "",
        myString.Split(' ').Select(s=>s.PadRight(N-s.Length)));