Replace Multiple String Elements in C#

问题

Is there a better way of doing this...

MyString.Trim().Replace("&", "and").Replace(",", "").Replace("  ", " ")
         .Replace(" ", "-").Replace("'", "").Replace("/", "").ToLower();

I've extended the string class to keep it down to one job but is there a quicker way?

public static class StringExtension
{
    public static string clean(this string s)
    {
        return s.Replace("&", "and").Replace(",", "").Replace("  ", " ")
                .Replace(" ", "-").Replace("'", "").Replace(".", "")
                .Replace("eacute;", "é").ToLower();
    }
}

Just for fun (and to stop the arguments in the comments) I've shoved a gist up benchmarking the various examples below.

https://gist.github.com/ChrisMcKee/5937656

The regex option scores terribly; the dictionary option comes up the fastest; the long winded version of the stringbuilder replace is slightly faster than the short hand.

回答1:

Quicker - no. More effective - yes, if you will use the StringBuilder class. With your implementation each operation generates a copy of a string which under circumstances may impair performance. Strings are immutable objects so each operation just returns a modified copy.

If you expect this method to be actively called on multiple Strings of significant length, it might be better to "migrate" its implementation onto the StringBuilder class. With it any modification is performed directly on that instance, so you spare unnecessary copy operations.

public static class StringExtention
{
    public static string clean(this string s)
    {
        StringBuilder sb = new StringBuilder (s);

        sb.Replace("&", "and");
        sb.Replace(",", "");
        sb.Replace("  ", " ");
        sb.Replace(" ", "-");
        sb.Replace("'", "");
        sb.Replace(".", "");
        sb.Replace("eacute;", "é");

        return sb.ToString().ToLower();
    }
}

回答2:

Maybe a little more readable?

    public static class StringExtension {

        private static Dictionary<string, string> _replacements = new Dictionary<string, string>();

        static StringExtension() {
            _replacements["&"] = "and";
            _replacements[","] = "";
            _replacements["  "] = " ";
            // etc...
        }

        public static string clean(this string s) {
            foreach (string to_replace in _replacements.Keys) {
                s = s.Replace(to_replace, _replacements[to_replace]);
            }
            return s;
        }
    }

Also add New In Town's suggestion about StringBuilder...

回答3:

this will be more efficient:

public static class StringExtension
{
    public static string clean(this string s)
    {
        return new StringBuilder(s)
              .Replace("&", "and")
              .Replace(",", "")
              .Replace("  ", " ")
              .Replace(" ", "-")
              .Replace("'", "")
              .Replace(".", "")
              .Replace("eacute;", "é")
              .ToString()
              .ToLower();
    }
}

回答4:

If you are simply after a pretty solution and don't need to save a few nanoseconds, how about some LINQ sugar?

var input = "test1test2test3";
var replacements = new Dictionary<string, string> { { "1", "*" }, { "2", "_" }, { "3", "&" } };

var output = replacements.Aggregate(input, (current, replacement) => current.Replace(replacement.Key, replacement.Value));

回答5:

There is one thing that may be optimized in the suggested solutions. Having many calls to Replace() makes the code to do multiple passes over the same string. With very long strings the solutions may be slow because of CPU cache capacity misses. May be one should consider replacing multiple strings in a single pass.

回答6:

Another option using linq is

[TestMethod]
public void Test()
{
  var input = "it's worth a lot of money, if you can find a buyer.";
  var expected = "its worth a lot of money if you can find a buyer";
  var removeList = new string[] { ".", ",", "'" };
  var result = input;

  removeList.ToList().ForEach(o => result = result.Replace(o, string.Empty));

  Assert.AreEqual(expected, result);
}

回答7:

I'm doing something similar, but in my case I'm doing serialization/De-serialization so I need to be able to go both directions. I find using a string[][] works nearly identically to the dictionary, including initialization, but you can go the other direction too, returning the substitutes to their original values, something that the dictionary really isn't set up to do.

Edit: You can use Dictionary<Key,List<Values>> in order to obtain same result as string[][]

回答8:

string input = "it's worth a lot of money, if you can find a buyer.";
for (dynamic i = 0, repl = new string[,] { { "'", "''" }, { "money", "$" }, { "find", "locate" } }; i < repl.Length / 2; i++) {
    input = input.Replace(repl[i, 0], repl[i, 1]);
}

来源：https://stackoverflow.com/questions/1321331/replace-multiple-string-elements-in-c-sharp

标签

string

refactoring

immutability