System Collections Generic C# by API

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
public class MainClass
{
    public static void Main()
    {
        IDictionary salaryMap = new Dictionary();
        salaryMap.Add("S", 60.5M);
        salaryMap.Add("W", 10.0M);
        salaryMap.Add("J", 30.99M);
        
        salaryMap.Remove("W");
    }
}