In this article, we’ll understand the interfaces (
IList) available for holding and querying the data.
- IEnumerable exists in
- IEnumerable is the most generic item of all and a core interface that is used to iterate over a collection of the specified type.
- IEnumerable provides an Enumerator for accessing the collection.
- IEnumerable is forward only collection like LinkedList. It doesn’t move between items or backward, i.e. one can't get at the fifth item without passing the first four items.
- It is a read-only collection and it doesn't support adding or removing items.
- IEnumerable is best to query data from in-memory collections like List, Array, etc.
- It mainly implements two methods:
MoveNext: This method tells whether there are more records to move on or not.
GetCurrent: This method returns the current record from the collection.
- IEnumerable still might use deferred execution and also supports further filtering.
- IEnumerable does not run query until it is requested by iteration or enumerator.
- Using IEnumerable we can find out the no of elements in the collection after iterating the collection.
- IQueryable exists in
- IQueryable extends the
- IQueryable allows deferred query execution i.e. query generated through IQueryable isn't executed until you iterate, enumerate, or add any method such as
- IQueryable enables a variety of interesting deferred execution scenarios such as paging and composition-based queries.
- IQueryable best suits remote data sources, like a DB or web service.
- IQueryable is particularly used for LINQ queries.
- IQueryable doesn’t support custom comparer, like any sting method such as
- IQueryable is not a good place to handle errors, so one must take care while writing complex queries.
- ICollection exists in
- ICollection implements the
- ICollection is the base of
- It is considered the most basic type for collections and is used to manipulate generic collections.
- As it implements the
IEnumerableinterface so it also implements methods
GetCurrent, so with this interface you can iterate through the collection.
- ICollection also has its own methods (apart from
Add: It adds a record at the end of the collection
Remove: It removes the specified item from the collection
Contains: It’s a boolean type method that tells whether the collection contains the specified item or not.
- Some collections that limit access to their elements, i.e. Queue or Stack class, directly implement the ICollection interface.
- ICollection is normally used where we define EF table relationships and we use this in the virtual keyword.
- ICollection doesn’t support indexing as IList does.
- IList exists in
- IList implementations fall into three categories:
Read-only: A read-only
IListcannot be modified.
Fixed-size: A fixed-size
IListdoes not allow the addition or removal of elements, but it allows the modification of existing elements.
Variable-size: A variable-size
IListallows the addition, removal, and modification of elements.
- IList is used where you need to iterate (read), modify and sort, order a collection
- With IList random element access is allowed i.e. you can access an element in a specific index in a list. For e.g. you can directly access an element at index 10 instead of first iterating through 0-9 elements.
- Like IEnumerable, IList is also in memory collection and helps you to query data from in-memory collections like List, Array etc.
- IList implements two interfaces
IEnumerable. So it also implements the methods of both the interfaces.
- IList also has its own methods like:
Insert: It inserts the given item at the specified Index.
RemoveAt: It removes the item from the specified Index.
IndexOf: It retrieves the item from the specified Index.
- IList can give you the no of elements in the collection without iterating the collection.
- IList supports deferred execution, but it doesn't support further filtering.
- IList supports custom comparer as the comparison is done inside the memory.
In this post, we saw some of the basic differences between
I hope this article will help you to choose a specific interface based on your demand. You can share your feedback, question, or comments about this article.
Originally published at http://diary-techies.blogspot.com on
March 14, 2014.