Looking for data in a secondary stream is a common requirement when the data you need comes from a source that is different from your main data—for example, if your data comes from a database, and you need to look up related data in an XML file. In this section, you will learn how to implement this kind of lookup through a simple exercise: We will have a list of European cities, and we will look for their cost of living indexes that are located in a different source. To do this, go through the following steps:
For this exercise, we will use a file with a list of European cities and their populations. The data was obtained from https://en.wikipedia.org/wiki/List_of_European_cities_by_population_within_city_limits ...
