C# using regexp while working with strings

Question

I have a string in this format "string1;string2;string3;...;stringn"
; as a delimiter
I need to delete some string value of which I know, say valueForDelete
I use string.Split(';') method to find my value, delete it and then create a new string without deleted value.
I'm wondering is it possible to make this process easy with regex?

Doesn't sound like anything string.Replace() couldn't do.

Hans Passant
– Hans Passant

2011-08-08 16:33:34 +00:00
Commented Aug 8, 2011 at 16:33 — Hans Passant
– Hans Passant, Commented Aug 8, 2011 at 16:33

Oskar Kjellin · Accepted Answer · 2011-08-08 19:47:44Z

4

var values = "string1;string2;string3;string4";
var cleanedValues = String.Join(";", 
         values.Split(';')
               .Where(x => x != "string3")
               .ToArray())

Regex is a useful tool, and could be used for this, but often hard to maintain. Something like the above would likely provide an easier to maintain solution. Regex can be tricky if your string also contain regex characters. As a bonus, this is easy to extend.

    static string CleanItUp(string values, params string[] removeMe)
    {
        return String.Join(";",
                   values.Split(';')
                         .Except(removeMe)
                         .ToArray());
    }

Used like.

var retString = CleanItUp("string1;string2;string3;", "string1", "string2");
// returns "string3"

edited Aug 8, 2011 at 19:47

Oskar Kjellin

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answered Aug 8, 2011 at 16:36

Travis

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10 Comments

Oskar Kjellin Over a year ago

Probably the most elegant solution

Corey Ogburn Over a year ago

Why use var there? You know that both of those variables are Strings.

Oskar Kjellin Over a year ago

Overuse of var is dangerous. I'm not a fan of it for simple types as strings

Travis Over a year ago

No good reason, I just use var almost everywhere. The type system takes care of it and I'm okay with that. However, that's a style thing, and ideally shouldn't detract from the overall solution. At least I hope ;)

Ken Wayne VanderLinde Over a year ago

@Corey: One reason var was invented exactly for when it's obvious what type the variable should be. In this case, it's obvious, so var is a good thing.

|

Oskar Kjellin · Accepted Answer · 2011-08-08 16:33:32Z

1

Why not just:

string s = "string1;string2;string3;valueForDelete;string4"
s = s.Replace("valueForDelete;", string.Empty).Replace("valueForDelete", string.Empty);

The second replace is for if the value is the last one.

answered Aug 8, 2011 at 16:33

Oskar Kjellin

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3 Comments

Daniel Hilgarth Over a year ago

If one of the other strings in the list contains (but is not equal to) "valueForDelete", it will be affected by this code.

Ken Wayne VanderLinde Over a year ago

Maybe try something like ";valueForDelete;", with another special case for if it's the first one in the string.

Oskar Kjellin Over a year ago

@Ken If I don't want to use if it wouldn't help

Corey Ogburn · Accepted Answer · 2011-08-08 16:39:13Z

0

However possible with RegEx, using Split and Join will be your easiest, most functional choice. If you had a more complex method of choosing what Strings to delete, you could use the Where clause.

String input = "string1;string2;string3";
String valueForDelete = "string2";
String[] parts = input.Split(';');
var allowed = parts.Where(str => !str.Equals(valueForDelete));
String output = String.Join(";", allowed);

If you are simply removing an exact value than String.Replace would be better.

answered Aug 8, 2011 at 16:39

Corey Ogburn

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Comments

Kirill Polishchuk · Accepted Answer · 2011-08-08 16:39:24Z

0

Use this Regex to find valueForDelete: (?<=;|^)valueForDelete(?=;|$)

const string Pattern = @"(?<=;|^)string3(?=;|$)";    
var s = "string1;string2;string3;string4;string5;";    
var res = Regex.Replace(s, Pattern, string.Empty);

edited Aug 8, 2011 at 16:39

answered Aug 8, 2011 at 16:33

Kirill Polishchuk

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Comments

paparazzo · Accepted Answer · 2011-08-08 16:41:10Z

0

Regex will do that but not sure that for what you are asking it would be faster. .Split is fast. If you were spitting on something more complex then you would have to use regex. I assume you are using StringBuilder to build the new string? String += is slow. When you new the StringBuilder make it the size you expect.

answered Aug 8, 2011 at 16:41

paparazzo

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1 Comment

paparazzo Over a year ago

I like the solution proposed by Travis. If it is a really big list list you might try my approach because it skips the ToArray. But good chance that approach proposed by Travis is still faster.

Rion Williams · Accepted Answer · 2011-08-08 16:42:10Z

0

For Replacement ensuring no other data is affected (using LINQ):

 string test = "string1;string2;string3;valueForDelete;stringn";
 test = String.Join(";", test.Split(';').Where(s => s != "valueForDelete"));

For simple replacement (using String.Replace()):

string test = "string1;string2;string3;valueForDelete;stringn";
test = test.Replace("valueForDelete;", "");

edited Aug 8, 2011 at 16:42

answered Aug 8, 2011 at 16:34

Rion Williams

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2 Comments

Ross Over a year ago

If one of the other strings in the list contains (but is not equal to) "valueForDelete", it will be affected by this code.

Oskar Kjellin Over a year ago

Also, this will result in an empty value; "string1;string2;string3;;stringn";

CaffGeek · Accepted Answer · 2011-08-08 16:44:22Z

0

Couldn't you just say

 var myString = "string1;string2;string3;string4;string5;";
 myString = myString.Replace("string3;", "");

The result would be a myString with the value "string1;string2;string4;string5;"

EDIT: Created as a regex

public static Regex regex = new Regex("(?:^|;)string3(;|$)", 
    RegexOptions.CultureInvariant | RegexOptions.Compiled
    );

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

...only flaw I see at the moment is if myString = "string3"; it results in myString = ";";

edited Aug 8, 2011 at 16:44

answered Aug 8, 2011 at 16:33

CaffGeek

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2 Comments

Ross Over a year ago

If one of the other strings in the list ends with (but is not equal to) "string3;", it will be affected by this code.

Daniel Hilgarth Over a year ago

If string3 would be the last one in the list this wouldn't work.

Elliott · Accepted Answer · 2011-08-08 16:52:04Z

0

Why Can't you just do this?

        public static string Replace(string input)
        {
            input = input.Replace("valueToDelete;", "");
            return input ;
        }

answered Aug 8, 2011 at 16:52

Elliott

1

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