using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.IO;
public class Test
{
	public static void Main()
	{
		string body = "hello [context.world]!! hello [context.anotherworld] and [context.text]";
		Dictionary<string, string> dyn = new Dictionary<string, string>(){ 
				{"world", "earth"}, {"anotherworld", "mars"}
		};
		Console.WriteLine(Regex.Replace(body, @"\[context\.(\w+)]", 
			m => dyn.ContainsKey(m.Groups[1].Value) ? dyn[m.Groups[1].Value] : m.Value));
	}
 
}

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