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Lists
Working with Ranges

So far we have added, accessed, and removed single elements in a list. What if we wanted to add, access, or remove multiple elements at once?

In the world of lists we call a subsequence of elements a range. For example, this list has 5 elements:

[ "first", "second", "third", "fourth", "fifth" ]

We can say the range of elements from index 1 to 3 is:

[ "second", "third", "fourth" ]

Here are four common range-related methods:

  • AddRange() — takes an array or list as an argument. Adds the values to the end of the list. Returns nothing.
  • InsertRange() — takes an int and array or list as an argument. Adds the values at the int index. Returns nothing.
  • RemoveRange() — takes two int values. The first int is the index at which to begin removing and the second int is the number of elements to remove. Returns nothing.
  • GetRange() — takes two int values. The first int is the index of the first desired element and the second int is the number of elements in the desired range. Returns a list of the same type.

Here is each one in action:

List<string> places = new List<string> { "first", "second" }; places.AddRange(new string[] { "fifth", "sixth" }); // List is "first", "second", "fifth", "sixth" ] places.InsertRange(2, new string[] { "third", "fourth"}); // List is [ "first", "second", "third", "fourth", "fifth", "sixth" ] places.RemoveRange(4, 2); // List is [ "first", "second", "third", "fourth" ] List<string> newPlaces = places.GetRange(0, 3); // New list is [ "first", "second", "third" ]

You don’t need to memorize these methods, but you should be familiar with the concept of ranges! You can always look up the methods again in the Microsoft documentation.

Instructions

1.

Use GetRange() to get the first three elements in the marathons list.

Store the result in a new list variable called topMarathons.

2.

Loop through the topMarathons list and print each value to the console.

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