Using RegEx in Dictionary

Question

I'm new to C#, and it looks I need to use Regex with Dictionary<string, Action>

The below working example with me, as testing of understanding the Regex in C#:

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

public class Program
{


    public static void Main()
    {

        string sPattern = "word1|word2";
        string input = "word2";

        Match result = Regex.Match(input, sPattern);

        Console.WriteLine(result);
    }
}

I tried to include it in Dictionary as below, but failed:

var functions = new Dictionary<Match, Action>();
functions.Add(Regex.Match(string, sPattern), CountParameters);

Action action;
if (functions.TryGetValue("word1|word2", out action)) {action.Invoke(); }

It gave me invalid expression string at Regex.Match(string, sPattern) and cannot convert string to Match at .TryGetValue("word1|word2")

UPDATE

I restructured my code like below, so I've no compiling error, but nothing is printed out as a result:

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

public class Program
{


    public static void Main()
    {

        string sPattern1 = "word1|word2";
        string sPattern2 = "word3|word4";

        string input = "word2";

        var functions = new Dictionary<string, Action>();
        functions.Add("word1", CountParameters);
        functions.Add("word3", SomeOtherMethodName);

        Action action;
        if (functions.TryGetValue((Regex.Match(input, sPattern1)).ToString(), out action))
        {
            action.Invoke();
        }
        else
        {
            // No function with that name
        }

    }


    public static void CountParameters()
    {
    Console.WriteLine("Fn 1");
    }

    public static void SomeOtherMethodName()
    {
    Console.WriteLine("Fn 2");
    }
}

The above is working if string input = "word1"; but not working if string input = "word2"; while the RegEx should consider both word1 and word2 as the same based on the string sPattern = "word1|word2";

UPDATE 2

In case it was not clear enough, the output of the above should be:

Executing CountParameters in case the input is word1 or word2, as the RegEx should consider them the same considering the | used in the pattern above.
Executing SomeOtherMethodName in case the input is word3 or word4, as the RegEx should consider them the same considering the | used in the pattern above.

and so on, in case I added more RegEx expression using the OR which is |

Andrei Tătar · Accepted Answer · 2016-11-06 08:36:36Z

1

I think you want something like this:

var input = "word2";
var functions = new Dictionary<Regex, Action>
{
    {new Regex("word1|word2"), CountParameters}
};
functions.FirstOrDefault(f => f.Key.IsMatch(input)).Value?.Invoke();

answered Nov 6, 2016 at 8:36

Andrei Tătar

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3 Comments

Hasan A Yousef Over a year ago

Can you elaborate more pls, what if my Dictionary have many pairs, like:

var functions = new Dictionary<Regex, Action> 		{ 			{new Regex("word1|word2"), CountParameters}, 			{new Regex("word3|word4"), SomeOtherMethodName} 		};

Andrei Tătar Over a year ago

It will execute the action assigned to the first found regular expression that matches your input.

Hasan A Yousef Over a year ago

I understood the ?. is a Null-conditional Operators, but what if I want to execute a command or print an error msg, is there a way to use TryGetValue here?

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