Interfaces

System.Collections.IEnumerator

Added in .NET 1.1

System.Collections.IEnumerable

Added in .NET 1.1
This is the minimum functionality and just lets you traverse in a forward direction.
This lets you perform a "foreach" on the collection.
This lets you support collection initializers.

System.Collections.ICollection

Added in .NET 1.1
This interface extended the IEnumerable interface.
This is the medium functionality and gives you foreach and a count
The ICollection interface is the base interface for classes in the System.Collections namespace.

System.Collections.IList

Added in .NET 1.1
This interface extended the ICollection interface.
This is the maximum functionality and gives you foreach, count, index/key, add, remove, contains, clear

System.Collections.IDictionary

Added in .NET 1.1
This interface extended the ICollection interface.
This is the maximum functionality and gives you foreach, count, index/key, add, remove, contains, clear
The IDictionary interface is the base interface for standard collections of key/value pairs.
Each element is a key/value pair stored in a DictionaryEntry object.

System.Collections.Generic.IComparer

Added in .NET 2.0
Provides additional comparison mechanisms
This allows you to provide ordering of your class on several fields or properties, ascending or descending order on the same field or both.

System.Collections.Generic.IEqualityComparer

Added in .NET 2.0
This interface is not implemented by the object itself but by an external class
This is an interface for an object that performs the comparison of two objects