Collections are similar to arrays: they store lists of objects. Hwever they provide a lot of usefull features not found in arrays (resizing, sorting etc). Microsoft .Net Framework provides severaltypes of collection classes_
- ArrayList Class -similar to array
- Remove method - removes an element
- Add method - adds a new element at the end
- Insert method - inserts a new element somewhere in the middle
- Stack Class - implements LIFO mechanism - like a stack
- Push - adds an element at the beginning
- Pop - removes an element from the end
- Hashtable Class - associative array - using other data types as element key
- ContainsKey - ckeck if the key is already taken
- elements are stored in DictionaryEntry object - used in foreach loop
- SortedList Class - similar to Hashtable - elements allways sorted (by using key)
Collections and arrays use similar syntax: elements can be added to collection in the following way:
SortedList peopleAge = new SortedList();
peopleAge["john"] = 31;
peopleAge["mary"] = 36;
peopleAge["James"] = 53;
peopleAge["Francesca"] = 18;
Iteration is done the same way as in arrays, with the difference that items are returned as DictionaryEntry, meaning that casting needs to be used.
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