LINQ vs. LSP

In response to my previous post about defensive programming , one of my readers sent me this question:

[One] A very well-known defensive programming script occurs when the input parameter is

 IEnumerable 
 
 public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … } 
  
 «   :     IEnumerable,    ,   .    ,  ICollection ,   ( ..:   ,     . ,   ,        .   ICollection   ,     ,  ?    -  .    ) .  ,  ,                  'publisher' (,       ). ,    ,   ,             .   ,       ,   . 
 « ,      ,        -, -   ,       IEnumerable .   ,      ,    – . 
 «   ,  ,     –   (      ),          . 
 
    . 
 
 . 
  IEnumerable        .NET.             , ,  ,      (LSP – Liskov Substitution Principle). ToArray()    ,    ,  ,   ,       .  ,    ToArray()   ,       . 
     ,      ToArray() –  ,    ,     IEnumerable. ,    «   »      ,   ,    ,   ,    ToArray() ( ToList() )  . ,   4-  IoC   :       .       :    ,      : 
 
 public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … } 
 ,     IEnumerable,            . 
 ,   ,      .      ,    ,  Publisher   .    ,       . 
    ,    Publisher       ,     ,           , ,   ,   -      . 
   ICollection ,    ,      ,      7     IEnumerable -   ,     . 
 
 LINQ  LSP 
          IQueryable  LSP,      LINQ to Objects, ,  LINQ     LSP. 
   LSP:             .     «»    ,      ,         ,        . ,    IEnumerable: 
 new[] { "foo", "bar", "baz" }; 
   : 
 public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } } 
 
    ,  ToArray() ( ToList() )       ,    ( )    . ,   , LSP- LINQ-  : 
 
 Any() AsEnumerable() Concat(IEnumerable) 
 DefaultIfEmpty() 
 DefaultIfEmpty(T) 
 Distinct (...) 
 Distinct(IEqualityComparer) (...) 
 ElementAt(int) 
 ElementAtOrDefault(int ) 
 First() 
 FirstOrDefault() 
 OfType() 
 Select(Func<TSource, TResult>) 
 Select(Func<TSource, int, TResult>) 
 SelectMany(Func<TSource, IEnumerable>) 
 SelectMany(Func<TSource, int, IEnumerable>) 
 SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>) 
 SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>) 
 Single() 
 SingleOrDefault() 
 Skip(int) 
 Take(int) 
 Where(Func<TSource, bool>) 
 Where(Func<TSource, int, bool>) 
 Zip(IEnumerable, Func<TFirst, TSecond, TResult>) 
 
 
       LINQ-,     .  ,      IEnumerable  , ..,   LSP   . 
       , ,  ,     ,        IReadOnlyCollection,    : ,    ,     .NET 4.5.  ,      . 
 
 . 
  ,  ,    IEnumerable  .      LSP- LINQ-,    (     -    ).           .NET 4.5,   IReadOnlyCollection   ,  IEnumerable.          ,    .NET 4.5,       (     -,   ,      ). 

IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

 IEnumerable 
 
 public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … } 
  
 «   :     IEnumerable,    ,   .    ,  ICollection ,   ( ..:   ,     . ,   ,        .   ICollection   ,     ,  ?    -  .    ) .  ,  ,                  'publisher' (,       ). ,    ,   ,             .   ,       ,   . 
 « ,      ,        -, -   ,       IEnumerable .   ,      ,    – . 
 «   ,  ,     –   (      ),          . 
 
    . 
 
 . 
  IEnumerable        .NET.             , ,  ,      (LSP – Liskov Substitution Principle). ToArray()    ,    ,  ,   ,       .  ,    ToArray()   ,       . 
     ,      ToArray() –  ,    ,     IEnumerable. ,    «   »      ,   ,    ,   ,    ToArray() ( ToList() )  . ,   4-  IoC   :       .       :    ,      : 
 
 public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … } 
 ,     IEnumerable,            . 
 ,   ,      .      ,    ,  Publisher   .    ,       . 
    ,    Publisher       ,     ,           , ,   ,   -      . 
   ICollection ,    ,      ,      7     IEnumerable -   ,     . 
 
 LINQ  LSP 
          IQueryable  LSP,      LINQ to Objects, ,  LINQ     LSP. 
   LSP:             .     «»    ,      ,         ,        . ,    IEnumerable: 
 new[] { "foo", "bar", "baz" }; 
   : 
 public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } } 
 
    ,  ToArray() ( ToList() )       ,    ( )    . ,   , LSP- LINQ-  : 
 
 Any() AsEnumerable() Concat(IEnumerable) 
 DefaultIfEmpty() 
 DefaultIfEmpty(T) 
 Distinct (...) 
 Distinct(IEqualityComparer) (...) 
 ElementAt(int) 
 ElementAtOrDefault(int ) 
 First() 
 FirstOrDefault() 
 OfType() 
 Select(Func<TSource, TResult>) 
 Select(Func<TSource, int, TResult>) 
 SelectMany(Func<TSource, IEnumerable>) 
 SelectMany(Func<TSource, int, IEnumerable>) 
 SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>) 
 SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>) 
 Single() 
 SingleOrDefault() 
 Skip(int) 
 Take(int) 
 Where(Func<TSource, bool>) 
 Where(Func<TSource, int, bool>) 
 Zip(IEnumerable, Func<TFirst, TSecond, TResult>) 
 
 
       LINQ-,     .  ,      IEnumerable  , ..,   LSP   . 
       , ,  ,     ,        IReadOnlyCollection,    : ,    ,     .NET 4.5.  ,      . 
 
 . 
  ,  ,    IEnumerable  .      LSP- LINQ-,    (     -    ).           .NET 4.5,   IReadOnlyCollection   ,  IEnumerable.          ,    .NET 4.5,       (     -,   ,      ). 

IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

 IEnumerable 
 
 public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … } 
  
 «   :     IEnumerable,    ,   .    ,  ICollection ,   ( ..:   ,     . ,   ,        .   ICollection   ,     ,  ?    -  .    ) .  ,  ,                  'publisher' (,       ). ,    ,   ,             .   ,       ,   . 
 « ,      ,        -, -   ,       IEnumerable .   ,      ,    – . 
 «   ,  ,     –   (      ),          . 
 
    . 
 
 . 
  IEnumerable        .NET.             , ,  ,      (LSP – Liskov Substitution Principle). ToArray()    ,    ,  ,   ,       .  ,    ToArray()   ,       . 
     ,      ToArray() –  ,    ,     IEnumerable. ,    «   »      ,   ,    ,   ,    ToArray() ( ToList() )  . ,   4-  IoC   :       .       :    ,      : 
 
 public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … } 
 ,     IEnumerable,            . 
 ,   ,      .      ,    ,  Publisher   .    ,       . 
    ,    Publisher       ,     ,           , ,   ,   -      . 
   ICollection ,    ,      ,      7     IEnumerable -   ,     . 
 
 LINQ  LSP 
          IQueryable  LSP,      LINQ to Objects, ,  LINQ     LSP. 
   LSP:             .     «»    ,      ,         ,        . ,    IEnumerable: 
 new[] { "foo", "bar", "baz" }; 
   : 
 public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } } 
 
    ,  ToArray() ( ToList() )       ,    ( )    . ,   , LSP- LINQ-  : 
 
 Any() AsEnumerable() Concat(IEnumerable) 
 DefaultIfEmpty() 
 DefaultIfEmpty(T) 
 Distinct (...) 
 Distinct(IEqualityComparer) (...) 
 ElementAt(int) 
 ElementAtOrDefault(int ) 
 First() 
 FirstOrDefault() 
 OfType() 
 Select(Func<TSource, TResult>) 
 Select(Func<TSource, int, TResult>) 
 SelectMany(Func<TSource, IEnumerable>) 
 SelectMany(Func<TSource, int, IEnumerable>) 
 SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>) 
 SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>) 
 Single() 
 SingleOrDefault() 
 Skip(int) 
 Take(int) 
 Where(Func<TSource, bool>) 
 Where(Func<TSource, int, bool>) 
 Zip(IEnumerable, Func<TFirst, TSecond, TResult>) 
 
 
       LINQ-,     .  ,      IEnumerable  , ..,   LSP   . 
       , ,  ,     ,        IReadOnlyCollection,    : ,    ,     .NET 4.5.  ,      . 
 
 . 
  ,  ,    IEnumerable  .      LSP- LINQ-,    (     -    ).           .NET 4.5,   IReadOnlyCollection   ,  IEnumerable.          ,    .NET 4.5,       (     -,   ,      ). 
 IEnumerable 
 
 public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … } 
  
 «   :     IEnumerable,    ,   .    ,  ICollection ,   ( ..:   ,     . ,   ,        .   ICollection   ,     ,  ?    -  .    ) .  ,  ,                  'publisher' (,       ). ,    ,   ,             .   ,       ,   . 
 « ,      ,        -, -   ,       IEnumerable .   ,      ,    – . 
 «   ,  ,     –   (      ),          . 
 
    . 
 
 . 
  IEnumerable        .NET.             , ,  ,      (LSP – Liskov Substitution Principle). ToArray()    ,    ,  ,   ,       .  ,    ToArray()   ,       . 
     ,      ToArray() –  ,    ,     IEnumerable. ,    «   »      ,   ,    ,   ,    ToArray() ( ToList() )  . ,   4-  IoC   :       .       :    ,      : 
 
 public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … } 
 ,     IEnumerable,            . 
 ,   ,      .      ,    ,  Publisher   .    ,       . 
    ,    Publisher       ,     ,           , ,   ,   -      . 
   ICollection ,    ,      ,      7     IEnumerable -   ,     . 
 
 LINQ  LSP 
          IQueryable  LSP,      LINQ to Objects, ,  LINQ     LSP. 
   LSP:             .     «»    ,      ,         ,        . ,    IEnumerable: 
 new[] { "foo", "bar", "baz" }; 
   : 
 public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } } 
 
    ,  ToArray() ( ToList() )       ,    ( )    . ,   , LSP- LINQ-  : 
 
 Any() AsEnumerable() Concat(IEnumerable) 
 DefaultIfEmpty() 
 DefaultIfEmpty(T) 
 Distinct (...) 
 Distinct(IEqualityComparer) (...) 
 ElementAt(int) 
 ElementAtOrDefault(int ) 
 First() 
 FirstOrDefault() 
 OfType() 
 Select(Func<TSource, TResult>) 
 Select(Func<TSource, int, TResult>) 
 SelectMany(Func<TSource, IEnumerable>) 
 SelectMany(Func<TSource, int, IEnumerable>) 
 SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>) 
 SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>) 
 Single() 
 SingleOrDefault() 
 Skip(int) 
 Take(int) 
 Where(Func<TSource, bool>) 
 Where(Func<TSource, int, bool>) 
 Zip(IEnumerable, Func<TFirst, TSecond, TResult>) 
 
 
       LINQ-,     .  ,      IEnumerable  , ..,   LSP   . 
       , ,  ,     ,        IReadOnlyCollection,    : ,    ,     .NET 4.5.  ,      . 
 
 . 
  ,  ,    IEnumerable  .      LSP- LINQ-,    (     -    ).           .NET 4.5,   IReadOnlyCollection   ,  IEnumerable.          ,    .NET 4.5,       (     -,   ,      ). 
 IEnumerable 
 
 public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … } 
  
 «   :     IEnumerable,    ,   .    ,  ICollection ,   ( ..:   ,     . ,   ,        .   ICollection   ,     ,  ?    -  .    ) .  ,  ,                  'publisher' (,       ). ,    ,   ,             .   ,       ,   . 
 « ,      ,        -, -   ,       IEnumerable .   ,      ,    – . 
 «   ,  ,     –   (      ),          . 
 
    . 
 
 . 
  IEnumerable        .NET.             , ,  ,      (LSP – Liskov Substitution Principle). ToArray()    ,    ,  ,   ,       .  ,    ToArray()   ,       . 
     ,      ToArray() –  ,    ,     IEnumerable. ,    «   »      ,   ,    ,   ,    ToArray() ( ToList() )  . ,   4-  IoC   :       .       :    ,      : 
 
 public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … } 
 ,     IEnumerable,            . 
 ,   ,      .      ,    ,  Publisher   .    ,       . 
    ,    Publisher       ,     ,           , ,   ,   -      . 
   ICollection ,    ,      ,      7     IEnumerable -   ,     . 
 
 LINQ  LSP 
          IQueryable  LSP,      LINQ to Objects, ,  LINQ     LSP. 
   LSP:             .     «»    ,      ,         ,        . ,    IEnumerable: 
 new[] { "foo", "bar", "baz" }; 
   : 
 public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } } 
 
    ,  ToArray() ( ToList() )       ,    ( )    . ,   , LSP- LINQ-  : 
 
 Any() AsEnumerable() Concat(IEnumerable) 
 DefaultIfEmpty() 
 DefaultIfEmpty(T) 
 Distinct (...) 
 Distinct(IEqualityComparer) (...) 
 ElementAt(int) 
 ElementAtOrDefault(int ) 
 First() 
 FirstOrDefault() 
 OfType() 
 Select(Func<TSource, TResult>) 
 Select(Func<TSource, int, TResult>) 
 SelectMany(Func<TSource, IEnumerable>) 
 SelectMany(Func<TSource, int, IEnumerable>) 
 SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>) 
 SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>) 
 Single() 
 SingleOrDefault() 
 Skip(int) 
 Take(int) 
 Where(Func<TSource, bool>) 
 Where(Func<TSource, int, bool>) 
 Zip(IEnumerable, Func<TFirst, TSecond, TResult>) 
 
 
       LINQ-,     .  ,      IEnumerable  , ..,   LSP   . 
       , ,  ,     ,        IReadOnlyCollection,    : ,    ,     .NET 4.5.  ,      . 
 
 . 
  ,  ,    IEnumerable  .      LSP- LINQ-,    (     -    ).           .NET 4.5,   IReadOnlyCollection   ,  IEnumerable.          ,    .NET 4.5,       (     -,   ,      ). 

IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

 IEnumerable 
 
 public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … } 
  
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    . 
 
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 public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … } 
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 ,   ,      .      ,    ,  Publisher   .    ,       . 
    ,    Publisher       ,     ,           , ,   ,   -      . 
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 LINQ  LSP 
          IQueryable  LSP,      LINQ to Objects, ,  LINQ     LSP. 
   LSP:             .     «»    ,      ,         ,        . ,    IEnumerable: 
 new[] { "foo", "bar", "baz" }; 
   : 
 public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } } 
 
    ,  ToArray() ( ToList() )       ,    ( )    . ,   , LSP- LINQ-  : 
 
 Any() AsEnumerable() Concat(IEnumerable) 
 DefaultIfEmpty() 
 DefaultIfEmpty(T) 
 Distinct (...) 
 Distinct(IEqualityComparer) (...) 
 ElementAt(int) 
 ElementAtOrDefault(int ) 
 First() 
 FirstOrDefault() 
 OfType() 
 Select(Func<TSource, TResult>) 
 Select(Func<TSource, int, TResult>) 
 SelectMany(Func<TSource, IEnumerable>) 
 SelectMany(Func<TSource, int, IEnumerable>) 
 SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>) 
 SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>) 
 Single() 
 SingleOrDefault() 
 Skip(int) 
 Take(int) 
 Where(Func<TSource, bool>) 
 Where(Func<TSource, int, bool>) 
 Zip(IEnumerable, Func<TFirst, TSecond, TResult>) 
 
 
       LINQ-,     .  ,      IEnumerable  , ..,   LSP   . 
       , ,  ,     ,        IReadOnlyCollection,    : ,    ,     .NET 4.5.  ,      . 
 
 . 
  ,  ,    IEnumerable  .      LSP- LINQ-,    (     -    ).           .NET 4.5,   IReadOnlyCollection   ,  IEnumerable.          ,    .NET 4.5,       (     -,   ,      ). 

IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
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.
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public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

• IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).
• IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).
• IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

  IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).

  IEnumerable

public class Publisher { public Publisher(IEnumerable<Subscriber> subscribers) { // defensive copy -> good or bad? this.subscribers = subscribers.ToArray(); } // … }

« : IEnumerable, , . , ICollection , ( ..: , . , , . ICollection , , ? - . ) . , , 'publisher' (, ). , , , . , , .
« , , -, - , IEnumerable . , , – .
« , , – ( ), .

.

.
IEnumerable .NET. , , , (LSP – Liskov Substitution Principle). ToArray() , , , , . , ToArray() , .
, ToArray() – , , IEnumerable. , « » , , , , ToArray() ( ToList() ) . , 4- IoC : . : , :

public class Publisher { public Publisher(Subscriber[] subscribers) { this.subscribers = subscribers; } // … }
, IEnumerable, .
, , . , , Publisher . , .
, Publisher , , , , , - .
ICollection , , , 7 IEnumerable - , .

LINQ LSP
IQueryable LSP, LINQ to Objects, , LINQ LSP.
LSP: . «» , , , . , IEnumerable:
new[] { "foo", "bar", "baz" };
:
public class InfiniteStrings : IEnumerable<string> { public IEnumerator<string> GetEnumerator() { while (true) yield return "foo"; } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

, ToArray() ( ToList() ) , ( ) . , , LSP- LINQ- :

Any() AsEnumerable() Concat(IEnumerable)
DefaultIfEmpty()
DefaultIfEmpty(T)
Distinct (...)
Distinct(IEqualityComparer) (...)
ElementAt(int)
ElementAtOrDefault(int )
First()
FirstOrDefault()
OfType()
Select(Func<TSource, TResult>)
Select(Func<TSource, int, TResult>)
SelectMany(Func<TSource, IEnumerable>)
SelectMany(Func<TSource, int, IEnumerable>)
SelectMany(Func<TSource, IEnumerable>, Func<TSource, TCollection, TResult>)
SelectMany(Func<TSource, int, IEnumerable>, Func<TSource, TCollection, TResult>)
Single()
SingleOrDefault()
Skip(int)
Take(int)
Where(Func<TSource, bool>)
Where(Func<TSource, int, bool>)
Zip(IEnumerable, Func<TFirst, TSecond, TResult>)


LINQ-, . , IEnumerable , .., LSP .
, , , , IReadOnlyCollection, : , , .NET 4.5. , .

.
, , IEnumerable . LSP- LINQ-, ( - ). .NET 4.5, IReadOnlyCollection , IEnumerable. , .NET 4.5, ( -, , ).