using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var test = new Dictionary<string, string>();

        /*** ERROR 1 - Key Does not exist ***/

        //Console.WriteLine(test["test"]);

        /* If there's a possibility that the key has not been inserted to the dictionary, check if key exists first */

        if (!test.ContainsKey("test"))

            Console.WriteLine("Value does not exist");

        else

            Console.WriteLine(test["test"]);

        /*** Test 2 - Value already added ***/

        //test.Add("test", "value");

        //test.Add("test", "value");

        /* When adding/updating Dictionary entry, better to use indexer */

        test["test"] = "value1";

        test["test"] = "value2";

        if (!test.ContainsKey("test"))

            Console.WriteLine("Value does not exist");

        else

            Console.WriteLine(test["test"]);        

    }

}