Признаки равенства, сравнения и их отличия

IEquatable:

This interface is implemented by types whose values can be equated (for example, the numeric and string classes). A value type or class implements the Equals method to create a type-specific method suitable for determining equality of instances.

The IComparable<T> interface defines the CompareTo method, which determines the sort order of instances of the implementing type. The IEquatable<T> interface defines the Equals method, which determines the equality of instances of the implementing type.

bool Equals(
T other
)

IComparable:

This interface is implemented by types whose values can be ordered; for example, the numeric and string classes. A value type or class implements the CompareTo method to create a type-specific comparison method suitable for purposes such as sorting.

The IComparable<T> interface defines the CompareTo method, which determines the sort order of instances of the implementing type. The IEquatable<T> interface defines the Equals method, which determines the equality of instances of the implementing type.

int CompareTo(
T other
)

IEqualityComparer:

This interface allows the implementation of customized equality comparison for collections. That is, you can create your own definition of equality for type T, and specify that this definition be used with a collection type that accepts the IEqualityComparer<T> generic interface. In the .NET Framework, constructors of the Dictionary<TKey, TValue> generic collection type accept this interface.

bool Equals(
T x,
T y
)

Implementations are required to ensure that if the Equals method returns true for two objects x and y, then the value returned by the GetHashCode method for x must equal the value returned for y.

The Equals method is reflexive, symmetric, and transitive. That is, it returns true if used to compare an object with itself; true for two objects x and y if it is true for y and x; and true for two objects x and z if it is true for x and y and also true for y and z.

IComparer:

This interface is used with the List<T>.Sort and List<T>.BinarySearch methods. It provides a way to customize the sort order of a collection. Classes that implement this interface include the SortedDictionary<TKey, TValue> and SortedList<TKey, TValue> generic classes.

int Compare(
T x,
T y
)