替换字符串中的值

Question

I am looking to find matches in a string, perform an action on the match, and then replace the original match.

For example finding @yahoo in a string, looking on matching everything after the ampersand to the first white space. Of course there can be multiple values to match on in a single string so would be a for each match.

I'm thinking regex but am not sure on matching on everything after the ampersand to the first white space (the regex expression for this?). Or any other easier way of doing this?

Answer 1

For this:

looking on matching everything after the ampersand to the first white space

regexp is @\\S+ .

Reference: Character Classes .

Answer 2

Assuming you have your Regex correctly setup, you can utilize one of the overloads of Regex.Replace to include a MatchEvaluator delegate. The MatchEvaluator is a Func<Match,string> delegate (meaning any public string Method(Match match) method will work as input), with the return value being what you want to replace the original string with. The regex for the search is (@\\S+) which means "Match the @ symbol, followed by any non-whitespace character ( \\S ) at least once ( + ).

Regex.Replace(input, "(@\S+)", (match) => { /* Replace logic here. */ })

Running the above regex on the input @yahoo.com is going to be @simple for purposes of @matching. , it matches on @yahoo.com , @simple and @matching. (notice that it includes punctiation on the @matching. ).

Hope that helps!

Answer 3

If you're writing in C#, a regex is probably your best option. The code is quite simple

MatchCollection matches = Regex.Matches(/*input*/, /*pattern*/)
foreach (Match m in matches)
{
    /*Do work here*/
}

For learning regular expressions and the syntax associated, I used http://www.regular-expressions.info/tutorial.html to get started. A lot of good information in there, and easy to read.

Answer 4

For example:

string str = "@yahoo aaaa bbb";
string replacedStr = str.Replace("@yahoo", "replacement");

Look to documentation: string.Replace

Answer 5

Do you mean ampersand & or at-symbol @ ?

This should do what you need: &([\\S\\.]+)\\b

or for the at-symbol: @([\\S\\.]+)\\b

Answer 6

Try using String.Replace() function:

String x="lalala i like being @Yahoo , my Email is John@Yahoo.com";

x=x.Replace("@Yahoo","@Gmail");

X will be now : "lalala i like being @Gmail, my Email is John@Gmail.com";

To know where the next space after "@Yahoo", use location variable, with String.IndexOf() and String.LastIndexOf().

int location=x.IndexOf("@Yahoo");//gets the location of the first "@Yahoo" of the string.

int SpaceLoc=x.IndexOf("@Yahoo",location);// gets the location of the first white space after the first "@Yahoo" of the string.

Hope that helps.

Answer 7

I think a RegEx.Replace is your best bet. You can simply do something like this:

string input = "name@yahoo.com is my email address";
string output = Regex.Replace(input, @"@\S+", new MatchEvaluator(evaluateMatch));

And you just need to define the evaluateMatch method, such as:

private string evaluateMatch(Match m)
{
    switch(m.Value)
    {
        case "@yahoo.com": 
            return "@google.com";
            break;
        default:
            return "@other.com";
    }
}