C# (programming language)

This article is about a programming language. For other uses, see C-sharp (disambiguation).
The correct title of this article is C# (programming language). The substitution or omission of the # is because of technical restrictions.
C#
Paradigm multi-paradigm: structured, imperative, object-oriented, event-driven, task-driven, functional, generic, reflective, concurrent
Family C
Designed by Microsoft
Developer Microsoft
First appeared 2000 (2000)
Stable release 6.0 / July 20, 2015 (2015-07-20)
Typing discipline static, dynamic,[1] strong, safe, nominative, partially inferred
Platform Common Language Infrastructure
License CLR is proprietary, Mono compiler is dual GPLv3, MIT/X11 and libraries are LGPLv2, DotGNU is dual GPL and LGPLv2
Filename extensions .cs
Website msdn.microsoft.com/pt-br/vcsharp/default.aspx
Major implementations
Visual C#, .NET Framework, Mono, DotGNU
Dialects
Cω, Spec#, Polyphonic C#
Influenced by
C++,[2] Eiffel, Java,[2] Modula-3, Object Pascal,[3] ML, Icon, Haskell, Rust, Cω, F#[note 1]
Influenced
Chapel,[4] D, Dart,[5] F#, Hack, Java,[6][7] Kotlin, Monkey, Nemerle, Oxygene, Rust, Swift,[8] Vala

C#[note 2] (pronounced as see sharp) is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. It was developed by Microsoft within its .NET initiative and later approved as a standard by Ecma (ECMA-334) and ISO (ISO/IEC 23270:2006). C# is one of the programming languages designed for the Common Language Infrastructure.

C# is a general-purpose, object-oriented programming language.[9] Its development team is led by Anders Hejlsberg. The most recent version is C# 6.0, which was released on July 20, 2015.[10]

Design goals

The ECMA standard lists these design goals for C#:[9]

History

During the development of the .NET Framework, the class libraries were originally written using a managed code compiler system called Simple Managed C (SMC).[11][12] In January 1999, Anders Hejlsberg formed a team to build a new language at the time called Cool, which stood for "C-like Object Oriented Language".[13] Microsoft had considered keeping the name "Cool" as the final name of the language, but chose not to do so for trademark reasons. By the time the .NET project was publicly announced at the July 2000 Professional Developers Conference, the language had been renamed C#, and the class libraries and ASP.NET runtime had been ported to C#.

C#'s principal designer and lead architect at Microsoft is Anders Hejlsberg, who was previously involved with the design of Turbo Pascal, Embarcadero Delphi (formerly CodeGear Delphi, Inprise Delphi and Borland Delphi), and Visual J++. In interviews and technical papers he has stated that flaws in most major programming languages (e.g. C++, Java, Delphi, and Smalltalk) drove the fundamentals of the Common Language Runtime (CLR), which, in turn, drove the design of the C# language itself.

James Gosling, who created the Java programming language in 1994, and Bill Joy, a co-founder of Sun Microsystems, the originator of Java, called C# an "imitation" of Java; Gosling further said that "[C# is] sort of Java with reliability, productivity and security deleted."[14][15] Klaus Kreft and Angelika Langer (authors of a C++ streams book) stated in a blog post that "Java and C# are almost identical programming languages. Boring repetition that lacks innovation,"[16] "Hardly anybody will claim that Java or C# are revolutionary programming languages that changed the way we write programs," and "C# borrowed a lot from Java - and vice versa. Now that C# supports boxing and unboxing, we'll have a very similar feature in Java."[17] In July 2000, Anders Hejlsberg said that C# is "not a Java clone" and is "much closer to C++" in its design.[18]

Since the release of C# 2.0 in November 2005, the C# and Java languages have evolved on increasingly divergent trajectories, becoming somewhat less similar. One of the first major departures came with the addition of generics to both languages, with vastly different implementations. C# makes use of reification to provide "first-class" generic objects that can be used like any other class, with code generation performed at class-load time.[19] Furthermore, C# has added several major features to accommodate functional-style programming, culminating in the LINQ extensions released with C# 3.0 and its supporting framework of lambda expressions, extension methods, and anonymous types.[20] These features enable C# programmers to use functional programming techniques, such as closures, when it is advantageous to their application. The LINQ extensions and the functional imports help developers reduce the amount of "boilerplate" code that is included in common tasks like querying a database, parsing an xml file, or searching through a data structure, shifting the emphasis onto the actual program logic to help improve readability and maintainability.[21]

C# used to have a mascot called Andy (named after Anders Hejlsberg). It was retired on January 29, 2004.[22]

C# was originally submitted to the ISO subcommittee JTC 1/SC 22 for review,[23] under ISO/IEC 23270:2003,[24] was withdrawn and was then approved under ISO/IEC 23270:2006.[25]

Name

C-sharp musical note

The name "C sharp" was inspired by musical notation where a sharp indicates that the written note should be made a semitone higher in pitch.[26] This is similar to the language name of C++, where "++" indicates that a variable should be incremented by 1. The sharp symbol also resembles a ligature of four "+" symbols (in a two-by-two grid), further implying that the language is an increment of C++.[27]

Due to technical limitations of display (standard fonts, browsers, etc.) and the fact that the sharp symbol (U+266F ♯ MUSIC SHARP SIGN (HTML ♯)) is not present on the standard keyboard, the number sign (U+0023 # NUMBER SIGN (HTML #)) was chosen to represent the sharp symbol in the written name of the programming language.[28] This convention is reflected in the ECMA-334 C# Language Specification.[9] However, when it is practical to do so (for example, in advertising or in box art[29]), Microsoft uses the intended musical symbol.

The "sharp" suffix has been used by a number of other .NET languages that are variants of existing languages, including J# (a .NET language also designed by Microsoft that is derived from Java 1.1), A# (from Ada), and the functional programming language F#.[30] The original implementation of Eiffel for .NET was called Eiffel#,[31] a name retired since the full Eiffel language is now supported. The suffix has also been used for libraries, such as Gtk# (a .NET wrapper for GTK+ and other GNOME libraries) and Cocoa# (a wrapper for Cocoa).

Versions

Version Language specification Date .NET Framework Visual Studio
ECMA ISO/IEC Microsoft
C# 1.0 December 2002 April 2003 January 2002 January 2002 .NET Framework 1.0 Visual Studio .NET 2002
C# 1.2 October 2003 April 2003 .NET Framework 1.1 Visual Studio .NET 2003
C# 2.0 June 2006 September 2006 September 2005[note 3] November 2005 .NET Framework 2.0 Visual Studio 2005
C# 3.0 None[note 4] August 2007 November 2007

.NET Framework 2.0 (Except LINQ/Query Extensions)[32]
.NET Framework 3.0 (Except LINQ/Query Extensions)[32]
.NET Framework 3.5

 Visual Studio 2008
Visual Studio 2010
C# 4.0 April 2010 April 2010 .NET Framework 4 Visual Studio 2010
C# 5.0 In Progress[33] None[note 4] June 2013 August 2012 .NET Framework 4.5 Visual Studio 2012
Visual Studio 2013
C# 6.0 None[note 4] None July 2015 .NET Framework 4.6 Visual Studio 2015

Features added in versions

C# 2.0

C# 3.0

C# 4.0

C# 5.0[38]

C# 6.0

C# 7.0 proposals[41]

Syntax

Main article: C Sharp syntax

The core syntax of C# language is similar to that of other C-style languages such as C, C++ and Java. In particular:

Distinguishing features

Some notable features of C# that distinguish it from C, C+, C++, and Java where noted, are:

Portability

By design, C# is the programming language that most directly reflects the underlying Common Language Infrastructure (CLI).[42] Most of its intrinsic types correspond to value-types implemented by the CLI framework. However, the language specification does not state the code generation requirements of the compiler: that is, it does not state that a C# compiler must target a Common Language Runtime, or generate Common Intermediate Language (CIL), or generate any other specific format. Theoretically, a C# compiler could generate machine code like traditional compilers of C++ or Fortran.

Typing

C# supports strongly typed implicit variable declarations with the keyword var, and implicitly typed arrays with the keyword new[] followed by a collection initializer.

C# supports a strict Boolean data type, bool. Statements that take conditions, such as while and if, require an expression of a type that implements the true operator, such as the Boolean type. While C++ also has a Boolean type, it can be freely converted to and from integers, and expressions such as if(a) require only that a is convertible to bool, allowing a to be an int, or a pointer. C# disallows this "integer meaning true or false" approach, on the grounds that forcing programmers to use expressions that return exactly bool can prevent certain types of programming mistakes such as if (a = b) (use of assignment = instead of equality ==, which while not an error in C or C++, will be caught by the compiler anyway).

C# is more type safe than C++. The only implicit conversions by default are those that are considered safe, such as widening of integers. This is enforced at compile-time, during JIT, and, in some cases, at runtime. No implicit conversions occur between Booleans and integers, nor between enumeration members and integers (except for literal 0, which can be implicitly converted to any enumerated type). Any user-defined conversion must be explicitly marked as explicit or implicit, unlike C++ copy constructors and conversion operators, which are both implicit by default.

C# has explicit support for covariance and contravariance in generic types, unlike C++ which has some degree of support for contravariance simply through the semantics of return types on virtual methods.

Enumeration members are placed in their own scope.

The C# language does not allow for global variables or functions. All methods and members must be declared within classes. Static members of public classes can substitute for global variables and functions.

Local variables cannot shadow variables of the enclosing block, unlike C and C++.

Meta programming

Meta programming via C# attributes is part of the language. Many of these attributes duplicate the functionality of GCC's and VisualC++'s platform-dependent preprocessor directives.

Methods and functions

Like C++, and unlike Java, C# programmers must use the keyword virtual to allow methods to be overridden by subclasses.

Extension methods in C# allow programmers to use static methods as if they were methods from a class's method table, allowing programmers to add methods to an object that they feel should exist on that object and its derivatives.

The type dynamic allows for run-time method binding, allowing for JavaScript-like method calls and run-time object composition.

C# has support for strongly-typed function pointers via the keyword delegate. Like the Qt framework's pseudo-C++ signal and slot, C# has semantics specifically surrounding publish-subscribe style events, though C# uses delegates to do so.

C# offers Java-like synchronized method calls, via the attribute [MethodImpl(MethodImplOptions.Synchronized)], and has support for mutually-exclusive locks via the keyword lock.

Property

C# provides properties as syntactic sugar for a common pattern in which a pair of methods, accessor (getter) and mutator (setter) encapsulate operations on a single attribute of a class. No redundant method signatures for the getter/setter implementations need be written, and the property may be accessed using attribute syntax rather than more verbose method calls.

Namespace

A C# namespace provides the same level of code isolation as a Java package or a C++ namespace, with very similar rules and features to a package.

Memory access

In C#, memory address pointers can only be used within blocks specifically marked as unsafe, and programs with unsafe code need appropriate permissions to run. Most object access is done through safe object references, which always either point to a "live" object or have the well-defined null value; it is impossible to obtain a reference to a "dead" object (one that has been garbage collected), or to a random block of memory. An unsafe pointer can point to an instance of a value-type, array, string, or a block of memory allocated on a stack. Code that is not marked as unsafe can still store and manipulate pointers through the System.IntPtr type, but it cannot dereference them.

Managed memory cannot be explicitly freed; instead, it is automatically garbage collected. Garbage collection addresses the problem of memory leaks by freeing the programmer of responsibility for releasing memory that is no longer needed.

Exception

Checked exceptions are not present in C# (in contrast to Java). This has been a conscious decision based on the issues of scalability and versionability.[43]

Polymorphism

Unlike C++, C# does not support multiple inheritance, although a class can implement any number of interfaces. This was a design decision by the language's lead architect to avoid complication and simplify architectural requirements throughout CLI. When implementing multiple interfaces that contain a method with the same signature, C# allows implementing each method depending on which interface that method is being called through, or, like Java, allows implementing the method once, and have that be the one invocation on a call through any of the class's interfaces.

However, unlike Java, C# supports operator overloading. Only the most commonly overloaded operators in C++ may be overloaded in C#.

Functional programming

Though primarily an imperative language, C# 2.0 offered limited support for functional programming through first-class functions and closures in the form of anonymous delegates. C# 3.0 expanded support for functional programming with the introduction of a light weight syntax for lambda expressions, extension methods (an affordance for modules), and a list comprehension syntax in the form of a "query comprehension" language.

Common type system

C# has an unified type system. This unified type system is called Common Type System (CTS).[44]

An unified type system implies that all types, including primitives such as integers, are subclasses of the System.Object class. For example, every type inherits a ToString() method.

Categories of data types

CTS separates data types into two categories:[44]

  1. Reference types
  2. Value types

Instances of value types do not have referential identity nor referential comparison semantics - equality and inequality comparisons for value types compare the actual data values within the instances, unless the corresponding operators are overloaded. Value types are derived from System.ValueType, always have a default value, and can always be created and copied. Some other limitations on value types are that they cannot derive from each other (but can implement interfaces) and cannot have an explicit default (parameterless) constructor. Examples of value types are all primitive types, such as int (a signed 32-bit integer), float (a 32-bit IEEE floating-point number), char (a 16-bit Unicode code unit), and System.DateTime (identifies a specific point in time with nanosecond precision). Other examples are enum (enumerations) and struct (user defined structures).

In contrast, reference types have the notion of referential identity - each instance of a reference type is inherently distinct from every other instance, even if the data within both instances is the same. This is reflected in default equality and inequality comparisons for reference types, which test for referential rather than structural equality, unless the corresponding operators are overloaded (such as the case for System.String). In general, it is not always possible to create an instance of a reference type, nor to copy an existing instance, or perform a value comparison on two existing instances, though specific reference types can provide such services by exposing a public constructor or implementing a corresponding interface (such as ICloneable or IComparable). Examples of reference types are object (the ultimate base class for all other C# classes), System.String (a string of Unicode characters), and System.Array (a base class for all C# arrays).

Both type categories are extensible with user-defined types.

Boxing and unboxing

Boxing is the operation of converting a value-type object into a value of a corresponding reference type.[44] Boxing in C# is implicit.

Unboxing is the operation of converting a value of a reference type (previously boxed) into a value of a value type.[44] Unboxing in C# requires an explicit type cast. A boxed object of type T can only be unboxed to a T (or a nullable T).[45]

Example:

int foo = 42;         // Value type.
object bar = foo;     // foo is boxed to bar.
int foo2 = (int)bar;  // Unboxed back to value type.

Libraries

The C# specification details a minimum set of types and class libraries that the compiler expects to have available. In practice, C# is most often used with some implementation of the Common Language Infrastructure (CLI), which is standardized as ECMA-335 Common Language Infrastructure (CLI).

Examples

The following is a very simple C# program, a version of the classic "Hello world" example:

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, world!");
    }
}

The effect is to write the following text to the output console:

Hello, world!

Each line has a purpose:

using System;

The above line of code tells the compiler to use System as a candidate prefix for types used in the source code. In this case, when the compiler sees use of the Console type later in the source code, it tries to find a type named Console, first in the current assembly, followed by all referenced assemblies. In this case the compiler fails to find such a type, since the name of the type is actually System.Console. The compiler then attempts to find a type named System.Console by using the System prefix from the using statement, and this time it succeeds. The using statement allows the programmer to state all candidate prefixes to use during compilation instead of always using full type names.

class Program

Above is a class definition. Everything between the following pair of braces describes Program.

static void Main()

This declares the class member method where the program begins execution. The .NET runtime calls the Main method. (Note: Main may also be called from elsewhere, like any other method, e.g. from another method of Program.) The static keyword makes the method accessible without an instance of Program. Each console application's Main entry point must be declared static. Otherwise, the program would require an instance, but any instance would require a program. To avoid that irresolvable circular dependency, C# compilers processing console applications (like that above) report an error, if there is no static Main method. The void keyword declares that Main has no return value.

Console.WriteLine("Hello, world!");

This line writes the output. Console is a static class in the System namespace. It provides an interface to the standard input, output, and error streams for console applications. The program calls the Console method WriteLine, which displays on the console a line with the argument, the string "Hello world!".

A GUI example:

using System.Windows.Forms;

class Program
{
    static void Main()
    {
        MessageBox.Show("Hello, world!");
    }
}

This example is similar to the previous example, except that it generates a dialog box that contains the message "Hello, world!" instead of writing it to the console.

Standardization and licensing

In August 2000, Microsoft Corporation, Hewlett-Packard and Intel Corporation co-sponsored the submission of specifications for C# as well as the Common Language Infrastructure (CLI) to the standards organization Ecma International. In December 2001, ECMA released ECMA-334 C# Language Specification. C# became an ISO standard in 2003 (ISO/IEC 23270:2003 - Information technology — Programming languages — C#). ECMA had previously adopted equivalent specifications as the 2nd edition of C#, in December 2002.

In June 2005, ECMA approved edition 3 of the C# specification, and updated ECMA-334. Additions included partial classes, anonymous methods, nullable types, and generics (somewhat similar to C++ templates).

In July 2005, ECMA submitted to ISO/IEC JTC 1, via the latter's Fast-Track process, the standards and related TRs. This process usually takes 6–9 months.

The C# language definition and the CLI are standardized under ISO and Ecma standards that provide reasonable and non-discriminatory licensing protection from patent claims.

Microsoft has agreed not to sue open source developers for violating patents in non-profit projects for the part of the framework that is covered by the OSP.[46] Microsoft has also agreed not to enforce patents relating to Novell products against Novell's paying customers[47] with the exception of a list of products that do not explicitly mention C#, .NET or Novell's implementation of .NET (The Mono Project).[48] However, Novell maintains that Mono does not infringe any Microsoft patents.[49] Microsoft has also made a specific agreement not to enforce patent rights related to the Moonlight browser plugin, which depends on Mono, provided it is obtained through Novell.[50]

Implementations

The reference C# compiler is Microsoft Visual C#, which is open-source.[51]

Microsoft is leading the development of a new open-source C# compiler and set of tools, previously codenamed "Roslyn". The compiler, which is entirely written in managed code (C#), has been opened up and functionality surfaced as APIs. It is thus enabling developers to create refactoring and diagnostics tools.

Other C# compilers exist, often including an implementation of the Common Language Infrastructure and the .NET class libraries up to .NET 2.0:

See also

Notes

  1. ↑ for async
  2. ↑ By convention, a number sign is used for the second character in normal text; in artistic representations, sometimes a true sharp sign is used: C♯.
  3. ↑ The Microsoft C# 2.0 specification document only contains the new 2.0 features. For older features use the 1.2 specification above.
  4. 1 2 3 No ECMA or ISO/IEC specifications exist for C# 3.0, 4.0 or 5.0.

References

  1. ↑ Torgersen, Mads (October 27, 2008). "New features in C# 4.0". Microsoft. Retrieved October 28, 2008.
  2. 1 2 Naugler, David (May 2007). "C# 2.0 for C++ and Java programmer: conference workshop". Journal of Computing Sciences in Colleges 22 (5). Although C# has been strongly influenced by Java it has also been strongly influenced by C++ and is best viewed as a descendant of both C++ and Java.
  3. ↑ Hamilton, Naomi (October 1, 2008). "The A-Z of Programming Languages: C#". Computerworld. Retrieved February 12, 2010. We all stand on the shoulders of giants here and every language builds on what went before it so we owe a lot to C, C++, Java, Delphi, all of these other things that came before us. (Anders Hejlsberg)
  4. ↑ "Chapel spec (Acknowlegements)" (PDF). Cray Inc. 2015-10-01. Retrieved 2016-01-14.
  5. ↑ "Web Languages and VMs: Fast Code is Always in Fashion. (V8, Dart) - Google I/O 2013". Google. Retrieved 22 December 2013.
  6. ↑ Java 5.0 added several new language features (the enhanced for loop, autoboxing, varargs and annotations), after they were introduced in the similar (and competing) C# language
  7. ↑ Cornelius, Barry (December 1, 2005). "Java 5 catches up with C#". University of Oxford Computing Services. Retrieved June 18, 2014. In my opinion, it is C# that has caused these radical changes to the Java language. (Barry Cornelius)
  8. ↑ Lattner, Chris (2014-06-03). "Chris Lattner's Homepage". Chris Lattner. Retrieved 2014-06-03. The Swift language is the product of tireless effort from a team of language experts, documentation gurus, compiler optimization ninjas, and an incredibly important internal dogfooding group who provided feedback to help refine and battle-test ideas. Of course, it also greatly benefited from the experiences hard-won by many other languages in the field, drawing ideas from Objective-C, Rust, Haskell, Ruby, Python, C#, CLU, and far too many others to list.
  9. 1 2 3 C# Language Specification (PDF) (4th ed.). Ecma International. June 2006. Retrieved January 26, 2012.
  10. ↑ Lander, Rich (20 July 2015). "Announcing .NET Framework 4.6". .NET Blog. Microsoft.
  11. ↑ Zander, Jason (November 24, 2008). "Couple of Historical Facts". Retrieved February 23, 2009.
  12. ↑ Guthrie, Scott (November 28, 2006). "What language was ASP.Net originally written in?". Retrieved February 21, 2008.
  13. ↑ Hamilton, Naomi (October 1, 2008). "The A-Z of Programming Languages: C#". Computerworld. Retrieved October 1, 2008.
  14. ↑ Wylie Wong (2002). "Why Microsoft's C# isn't". CNET: CBS Interactive. Retrieved May 28, 2014.
  15. ↑ Bill Joy (February 7, 2002). "Microsoft's blind spot". cnet.com. Retrieved January 12, 2010.
  16. ↑ Klaus Kreft and Angelika Langer (2003). "After Java and C# - what is next?". Retrieved June 18, 2013.
  17. ↑ Klaus Kreft and Angelika Langer (July 3, 2003). "After Java and C# - what is next?". artima.com. Retrieved January 12, 2010.
  18. ↑ Osborn, John (August 1, 2000). "Deep Inside C#: An Interview with Microsoft Chief Architect Anders Hejlsberg". O'Reilly Media. Retrieved November 14, 2009
  19. ↑ "Generics (C# Programming Guide)". Microsoft. Retrieved March 21, 2011.
  20. ↑ Don Box and Anders Hejlsberg (February 2007). "LINQ: .NET Language-Integrated Query". Microsoft. Retrieved March 21, 2011.
  21. ↑ Mercer, Ian (April 15, 2010). "Why functional programming and LINQ is often better than procedural code". abodit.com. Retrieved March 21, 2011.
  22. ↑ "Andy Retires". Dan Fernandez's Blog. Blogs.msdn.com. January 29, 2004. Retrieved October 4, 2012.
  23. ↑ "Technical committees - JTC 1/SC 22 - Programming languages, their environments and system software interfaces". ISO. Retrieved October 4, 2012.
  24. ↑ "ISO/IEC 23270:2003 - Information technology - C# Language Specification". Iso.org. August 23, 2006. Retrieved October 4, 2012.
  25. ↑ "ISO/IEC 23270:2006 - Information technology - Programming languages - C#". Iso.org. January 26, 2012. Retrieved October 4, 2012.
  26. ↑ Kovacs, James (September 7, 2007). "C#/.NET History Lesson". Retrieved June 18, 2009.
  27. ↑ Hejlsberg, Anders (October 1, 2008). "The A-Z of Programming Languages: C#". Computerworld.
  28. ↑ "Microsoft C# FAQ". Microsoft. Retrieved March 25, 2008. Archived February 14, 2006, at the Wayback Machine.
  29. ↑ "Visual C#.net Standard" (JPEG). Microsoft. September 4, 2003. Retrieved June 18, 2009.
  30. ↑ "F# FAQ". Microsoft Research. Retrieved June 18, 2009. Archived February 18, 2009, at the Wayback Machine.
  31. ↑ Simon, Raphael; Stapf, Emmanuel; Meyer, Bertrand (June 2002). "Full Eiffel on the .NET Framework". Microsoft. Retrieved June 18, 2009.
  32. 1 2 "Using C# 3.0 from .NET 2.0". Danielmoth.com. May 13, 2007. Retrieved October 4, 2012.
  33. ↑ "Mono and Roslyn". Tirania Blog. Miguel de Icaza. Retrieved 9 April 2014.Work in progress for C# 5.0.
  34. 1 2 3 4 5 6 7 8 9 10 "What's new in the C# 2.0 Language and Compiler". Microsoft Developer Network. Microsoft. Retrieved 11 June 2014.
  35. 1 2 3 4 5 6 7 8 Hejlsberg, Anders; Torgersen, Mads. "Overview of C# 3.0". Microsoft Developer Network. MIcrosoft. Retrieved 11 June 2014.
  36. ↑ Ghosh, Wriju. "C# 3.0 : Partial Methods". MSDN Blogs. Microsoft. Retrieved 11 June 2014.
  37. 1 2 3 4 Burrows, Chris. "C# 4.0 - New C# Features in the .NET Framework 4". Microsoft Developer Network. Microsoft. Retrieved 11 June 2014.
  38. ↑ Hejlsberg, Anders. "Future directions for C# and Visual Basic". C# lead architect. Microsoft. Retrieved September 21, 2011.
  39. 1 2 "An Introduction to New Features in C# 5.0". MSDN Blogs. Microsoft. Retrieved 11 June 2014.
  40. 1 2 3 4 5 6 7 8 9 10 "Language feature implementation status". github. Microsoft. Retrieved 13 February 2015.
  41. ↑ "C# 7 Work List of Features · Issue #2136 · dotnet/roslyn". GitHub. Retrieved 2016-01-11.
  42. ↑ Visual Studio 2010 and .NET 4 Six-in-One. Wrox Press. 2010. ISBN 0470499486.
  43. ↑ Venners, Bill; Eckel, Bruce (August 18, 2003). "The Trouble with Checked Exceptions". Retrieved March 30, 2010.
  44. 1 2 3 4 Archer, Tom (2001). "Part 2, Chapter 4: The Type System". Inside C#. Redmond, Washington: Microsoft Press. ISBN 0-7356-1288-9.
  45. ↑ Lippert, Eric (March 19, 2009). "Representation and Identity". Fabulous Adventures In Coding. Blogs.msdn.com. Retrieved October 4, 2012.
  46. ↑ "Patent Pledge for Open Source Developers".
  47. ↑ "Patent Cooperation Agreement - Microsoft & Novell Interoperability Collaboration". Microsoft. November 2, 2006. Retrieved July 5, 2009. Microsoft, on behalf of itself and its Subsidiaries (collectively "Microsoft"), hereby covenants not to sue Novell's Customers and Novell's Subsidiaries' Customers for infringement under Covered Patents of Microsoft on account of such a Customer's use of specific copies of a Covered Product as distributed by Novell or its Subsidiaries (collectively "Novell") for which Novell has received Revenue (directly or indirectly) for such specific copies; provided the foregoing covenant is limited to use by such Customer (i) of such specific copies that are authorized by Novell in consideration for such Revenue, and (ii) within the scope authorized by Novell in consideration for such Revenue.
  48. ↑ "Definitions". Microsoft. November 2, 2006. Retrieved July 5, 2009.
  49. ↑ Steinman, Justin (November 7, 2006). "Novell Answers Questions from the Community". Retrieved July 5, 2009. We maintain that Mono does not infringe any Microsoft patents.
  50. ↑ "Covenant to Downstream Recipients of Moonlight - Microsoft & Novell Interoperability Collaboration". Microsoft. September 28, 2007. Retrieved March 8, 2008. "Downstream Recipient" means an entity or individual that uses for its intended purpose a Moonlight Implementation obtained directly from Novell or through an Intermediate Recipient... Microsoft reserves the right to update (including discontinue) the foregoing covenant... "Moonlight Implementation" means only those specific portions of Moonlight 1.0 or Moonlight 1.1 that run only as a plug-in to a browser on a Personal Computer and are not licensed under GPLv3 or a Similar License.
  51. ↑ https://github.com/dotnet/roslyn
  52. ↑ "Compatibility - Mono". Mono-project.com. December 19, 2011. Retrieved October 4, 2012.

Further reading

External links

Wikibooks has a book on the topic of: C Sharp Programming
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