difference between list and dictionary in c#

Question

Bikesh Srivastava · Answer

List and Dictionary - pretty different data structures which used for different purposes, List is simply a set of items and Dictionary is a set of key-value pairs. Dictionary is pretty useful when you have a set of complex objects and want to have fast access by let's say ObjectName/ObjectId, in this case you create IDictionary where key would be ObjectId and Value would be an object itself. Some differences: List persist order of the items, Dictionary does not List allow fast access by index List support built in QuickSort algorithm for fast data sorting Dictionary allows ~ O(1) time complexity to access an item (value) by a key

Amit Diwan · Answer

@Bikesh and @Mohammed Deeb's answers are completely copied from StackOverflow. Do add a reference if your are copying answers from other websites. I hope editors are keeping an eye on this.

Mayank · Answer

https://www.dotnetperls.com/dictionary-time

Khaja Moizuddin · Answer

Dictionary is a pair of key and value ie.int string ,we can store the values like 1, dotnet 2,Java 3,oracle etc. List is a collection which is used with collection of items like Array etc.

Technetshadow · Answer

Dictionaries map a key to a value, whereas a list just contains a collection of values. So really it comes down to list vs. dictionary. Do the items you want to put into a collection have some kind of unique identifier that could be used to sort them so they can be stored & retrieved faster? If the answer is yes, use Dictionary. If the answer is no, use List.

Mohammed Deeb Hammoudeh · Answer

IDictionary is for key->value maps, ICollection is for sets of similar objects. ICollection is an interface for collections of similar objects: the controls on a form, the elements in a list, the attributes in an XML tag, and so on. As of .NET 2.0, there's a generic version, so you can refer to a collection of integers as ICollection . IDictionary is an interface for mapping one type of object or value to another. It works like a real dictionary, or a phone book: you have a "key" in mind like a person’s name, and when you look it up, you get some information that’s identified by that key, like an address or phone number. Each key can only be listed once, although two different keys are still allowed to have the same value. This is also generic in .NET 2.0, so a dictionary whose keys are strings and whose values are integers would be IDictionary . A dictionary is actually a collection of key/value pairs: you can use an IDictionary as an ICollection > , and you can access the keys and values as separate collections with the Keys and Values properties. Both ICollection and IDictionary are unordered, meaning that although you can retrieve the elements in some order with the CopyTo method or a foreach loop, that order has no special meaning, and it might change for no apparent reason. That’s the main difference between ICollection and IList : a list lets you put items in specific positions, just like an array, and they stay there until you move them.