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Let's take a closer look at how to use the List class.
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So far we've seen how to create a list,
add items to it and
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access those items using their index.
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We can add items to the list at the time
it's created by using a collection
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initializer.
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We simply instantiate our list
exactly as we had before.
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Before typing the semi-colon we add
opening and closing curly braces here.
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We still need the ending semicolon though.
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Now we can list the items we want our list
to start out with just like we did with
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arrays.
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So I'll say Sue.
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Bill.
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Allen.
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Beth.
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And Mary.
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Notice that even though we've
only listed five items here,
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the capacity of the list is eight.
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This is because the collection initializer
actually just calls the list add method.
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This is exactly like creating the list and
then calling the add method five times.
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The list had two resize
itself to a capacity of eight
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when it got to the fifth item.
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Again this is a good time to give
the list an initial capacity and
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avoid some overhead.
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[BLANK AUDIO] So
we can say five right here.
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Another way to instantiate a list
is with another collection
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by passing it to the constructor.
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So let's create another
list called students2 and
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we'll say new list string.
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And we'll pass in the students
list we created before.
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Passing in another list essentially
makes a copy of the list.
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I could have passed in any
collection type here, in fact,
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passing in an array here is a good
way to convert an array into a list.
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We can convert a list to
an array by calling two array.
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So let's create a string array here.
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Call it studentArray.
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And set equal to students.Toarray.
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We can iterate through all of the items
in a list the same way we did with
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the arrays.
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We will use a foreach loop but
we could use a for
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loop for a while loop so
say foreach string student in students.
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And then we'll just print
them to the console.
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So I'll say console.writeline student.
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We can also insert items anywhere in
the list using the Insert method.
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So I'll say students.Insert.
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And here we specify the index that
we want to insert the new item at so
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I'll put something right it index 1.
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And will insert Frank.
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When we enter items into a list all
of the items after where we inserted
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the item get moved up.
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So Bill, Allen, Beth, and
Mary all had to be moved up.
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This is not a quick task if
there are a lot of items.
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Also if there isn't enough room to add
the item, then the list is resized.
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There are a couple of ways
to remove items from a list.
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If we know the index of the item
that we want to remove,
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then we can use the remove at method.
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Let's say Bill moved to another school so
we need to remove him from the list.
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If we happen to already know
that Bill is at index 2,
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we can say students.removeAt 2.
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Now if we take a look at students,
we can see that Bill is gone and
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all of the items after where Bill was
have been shifted back down in the list.
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Like arrays, lists are not optimized
to have items inserted into or
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removed from the middle of them.
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However, this usually isn't a big problem.
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You'll find that inserting and
deleting items from the middle of a list
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is actually not as common in everyday
programs as you might think.
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There are collections that
are designed to make adding and
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removing items much faster though.
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I'll mention some of these more
specialized collections near the end of
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this course.
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