Difference between array, arraylist, List, Hashtable, Dictionary and SortedList in c#

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Basic difference is that arrays are of fixed size. Whereas an ArrayList implements the list data structure and can dynamically grow. While arrays would be more performance that a list, a list would be far more flexible since you don't need to know the required size initially. Array - represents an old-school memory array - kind of like a alias for a normal type[] array. Can enumerate. Can't grow automatically. I would assume very fast insertion, retrieve and speed. ArrayList - automatically growing array. Adds more overhead. Can enum., probably slower than a normal array but still pretty fast. These are used a lot in .NET List - one of my favorites - can be used with generics, so you can have a strongly typed array, e.g. List . Other than that, acts very much like ArrayList. Hashtable - plain old hashtable. O(1) to O(n) worst case. Can enumerate the value and keys properties, and do key/val pairs. Dictionary - same as above only strongly typed via generics, such a...
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All about interface in c#.net

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An interface contains definitions for a group of related functionalities that a class or a struct can implement. You can define an interface by using the interface keyword, as the following example shows. 

interface IEquatable<T>      {          bool Equals(T obj);      }

To implement an interface member, the corresponding member of the implementing class must be public, 
non-static, and have the same name and signature as the interface member.

Quick overview of interface :

  • An interface is like an abstract base class. Any class or struct that implements the interface must implement all its members.
  • An interface can't be instantiated directly. Its members are implemented by any class or struct that implements the interface.
  • Interfaces can contain events, indexers, methods, and properties.
  • Interfaces contain no implementation of methods.
  • A class or struct can implement multiple interfaces. A class can inherit a base class and also implement one or more interfaces.


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