Question

How to check whether a user string contains any forbidden words from a list in C#

Answer 1

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

class Program
{
    // Fast O(1) lookup
    private static readonly HashSet<string> Forbidden = new(StringComparer.OrdinalIgnoreCase) {
        "badword",
        "evil",
        "kill",
        "nasty",
        "terrible"
    };

    public static bool ContainsForbidden(string input) {
        // Normalize: lowercase + split on non-alphanumeric
        var words = Regex.Split(input.ToLower(), "[^a-z0-9]+"); 
        
        foreach (var w in words) {
            if (Forbidden.Contains(w))
                return true;
        }

        return false;
    }

    static void Main()
    {
        string s = "This text contains a badword inside";

        if (ContainsForbidden(s))
            Console.WriteLine("Forbidden word detected");
        else
            Console.WriteLine("No forbidden words found");
    }
}


/*
run:

Forbidden word detected

*/

 

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