C#中的正则表达式包含"this"而不是"that"

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "This is an example string with this word.";
        string pattern = "this";

        // Check if the input contains the pattern
        if (Regex.IsMatch(input, pattern, RegexOptions.IgnoreCase))
        {
            Console.WriteLine("The input contains the pattern.");
        }
        else
        {
            Console.WriteLine("The input does not contain the pattern.");
        }
    }
}

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        string input = "This is an example string with this word.";
        string pattern = "this";

        // Find all matches of the pattern
        MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnoreCase);

        Console.WriteLine($"Found {matches.Count} matches:");
        foreach (Match match in matches)
        {
            Console.WriteLine(match.Value);
        }
    }
}