using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var expressions = new[] {

            @"First Param Value -p1 Second Param Value -p2[Third-Param-Value] -X ""-Fourth -Param -Value"" -pl LastParamValue Last Value",

            @"-p0 First Param Value -p1 Second Param Value -p2[Third-Param-Value] -X ""-Fourth -Param -Value"" -pl LastParamValue Last Value",

            @"First Param Value -p1 Second Param Value -p2[Third-Param-Value] -p3[nested [param ""value""] ] -p4{nested { -param "" } } -p5(nested ( () -param ] ]""[) ) -X ""-Fourth -Param\"" -Value"" -pl ""Last Param Value"" Last Value",

        };

        var tokensRegex = new Regex(@"

(?x)

  \s*(?<token> (?>(?'o'\[)[^][]*)+(?>[^][]*(?'-o'\]))+ )\s*  # balanced [...] group

| \s*(?<token> (?>(?'o'\{)[^{}]*)+(?>[^{}]*(?'-o'\}))+ )\s*  # balanced {...} group

| \s*(?<token> (?>(?'o'\()[^()]*)+(?>[^()]*(?'-o'\)))+ )\s*  # balanced (...) group

| \s*(?<token> ""(?:\\""|[^""])*"" )\s*   # quoted group with possible escaped quotes within

| \s*(?<token> -[^\s""({[]+ )             # parameter name

| (?<token> \s*\S+\s* )                   # parameter value part not in group/quotes

");

        foreach (var expression in expressions)

        {

            var paramDict = new Dictionary<string, string>();

            var currParam = "<FIRST>";

            var currValues = new List<string>();

            var lastParam = currParam;

            foreach (var token in tokensRegex.Matches(expression)

                .Cast<Match>().Select(m => m.Groups["token"].Value))

            {

                if (token.StartsWith("-"))

                {

                    // This is a paramater name. Store collected value

                    // for the previous one and reset currXXX

                    if (currParam == "<FIRST>" && currValues.Count == 0)

                    {

                        // The first param has its own name so don't add the default one.

                        // Set the param name only

                        currParam = token;

                    }

                    else

                    {

                        paramDict.Add(currParam, string.Join("", currValues));

                        currParam = token;

                        currValues = new List<string>();

                    }

                }

                else

                {

                    currValues.Add(token);

                }

            }

​

            // If the last value list has more that one item, set the first item

            // as the last param value and the rest as the last value.

            if (currValues.Count > 1)

            {

                paramDict[currParam] = currValues[0];

                paramDict["<LAST>"] = string.Join("", currValues.Skip(1));

            }

​

            // Output the dictionary

            Console.WriteLine("Expression parsed: {0}", expression);

            foreach (var kvp in paramDict)

                Console.WriteLine("\t{0}\t => {1}", kvp.Key, kvp.Value);

        }

    }

}