class Customers {
/**
* Remeber to implement the IEnumerable interface so that you can use
* an instance of this class on a foreach.
*/

  // .......
  //The return type has to change to CoffeeType as well.
  public CoffeeType this[string sNmae]{
    /**
    * The following is fine. Not sure if you need the ToList() at the
    * end though.
    */
    //Add .Coffee at the end to return CoffeeType.
    get { return lstCustomers.Where(s => s.Name == sName).ToList()[0].Coffee; }

    /**
    * This is where you need to make some changes.
    */

    set {
      //Get collection
      var customers = lstCustomers.Where(s => s.Name == sName);

      //Check if there is anything in the collection.
      if( customers.Exists()){
        //Get first value
        var cust = customers.First();
        cust.Coffee = value;
      }
      else {
        var cust = new CCustomer(sName, value); //First Parameter is Name and second is CoffeeType.
      }
    }
  }
  // .......

}