test.cs

public static List<string> ExtractSentences(string input)
{
	List<string> sentences = new List<string>();

	// Use regular expression to split the input string into sentences but keep white spaces
	string pattern = @"([.!?])";

	// split the input string into sentences with the delimiters
	string[] splitSentences = Regex.Split(input, pattern);
	
	// Trim each sentence and remove empty strings
	foreach (string sentence in splitSentences)
	{
		sentences.Add(sentence);
	}

	return sentences;
}