Useful Interfaces in .NET

IEnumerable<T>

Exposes the enumerator which supports iteration over a collection of a specified type. This interface can be found under System.Collections.Generic namespace. 

This is the base interface for collections in Collections.Generic namespace such as  List<T>, Dictionary<TKey, TValue> etc.. For non-generic .NET has IEnumerable.

IEnumerable<T> has a single method GetEnumerator which you must implement when implementing the interface. This returns a IEnumerator<T> object.

MSDN Documentation

IEnumerable 

Just like its generic version, exposes an enumerator.

Difference between IEnumerable vs IEnumerable<T> 

MSDN Documentation 

IComparable

IComparer

IDisposable

IQuerable


IEqutable


IList


IDictionary