Use a String.Format format and transform its output to its inputs?

ParseExact for Strings?

 

The DateTime.ParseExact() method has come in handy on a number of occasions. I really wish there was something similar for strings as sometimes you need to grab specific components of a string. You can use regex directly but that seems a little cumbersome. So here is an extension method that works like the DateTime.ParseExact() but returns an array of strings.

string value = "2/17/2009 10:57:42 AM...Executing file 26 of 81 files";

string[] parts = value.ParseExact("{0}...Executing file {1} of {2} files");

foreach (string part in parts)

    Console.WriteLine(part);

Console.ReadKey();

Implementation:

public static class StringExtensions

{

    public static string[] ParseExact(

        this string data, 

        string format)

    {

        return ParseExact(data, format, false);

    }



    public static string[] ParseExact(

        this string data, 

        string format, 

        bool ignoreCase)

    {

        string[] values;



        if (TryParseExact(data, format, out values, ignoreCase))

            return values;

        else

            throw new ArgumentException("Format not compatible with value.");

    }



    public static bool TryExtract(

        this string data, 

        string format, 

        out string[] values)

    {

        return TryParseExact(data, format, out values, false);

    }



    public static bool TryParseExact(

        this string data, 

        string format, 

        out string[] values, 

        bool ignoreCase)

    {

        int tokenCount = 0;

        format = Regex.Escape(format).Replace("\\{", "{");



        for (tokenCount = 0; ; tokenCount++)

        {

            string token = string.Format("{{{0}}}", tokenCount);

            if (!format.Contains(token)) break;

            format = format.Replace(token,

                string.Format("(?'group{0}'.*)", tokenCount));

        }



        RegexOptions options = 

            ignoreCase ? RegexOptions.IgnoreCase : RegexOptions.None;



        Match match = new Regex(format, options).Match(data);



        if (tokenCount != (match.Groups.Count - 1))

        {

            values = new string[] { };

            return false;

        }

        else

        {

            values = new string[tokenCount];

            for (int index = 0; index < tokenCount; index++)

                values[index] = 

                    match.Groups[string.Format("group{0}", index)].Value;

            return true;

        }

    }

}

原帖：

http://blog.mikeobrien.net/2009/02/parseexact-for-strings.html