ISO/IEC 23270:2018
Information technology — Programming languages — C#
This specification describes the form and establishes the interpretation of programs written in the C# programming language. It describes:
— The representation of C# programs;
— The syntax and constraints of the C# language;
— The semantic rules for interpreting C# programs;
— The restrictions and limits imposed by a conforming implementation of C#.
This specification does not describe
— The mechanism by which C# programs are transformed for use by a data-processing system;
— The mechanism by which C# applications are invoked for use by a data-processing system;
— The mechanism by which input data are transformed for use by a C# application;
— The mechanism by which output data are transformed after being produced by a C# application;
— The size or complexity of a program and its data that will exceed the capacity of any specific data-processing system or the capacity of a particular processor;
— All minimal requirements of a data-processing system that is capable of supporting a conforming implementation.
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Table of Contents
Introduction
1. Scope
2. Normative references
3. Terms and definitions
4. Acronyms and abbreviations
5. General description
6. Conformance
7. Lexical structure
7.1 Programs
7.2 Grammars
7.2.1 General
7.2.2 Grammar notation
7.2.3 Lexical grammar
7.2.4 Syntactic grammar
7.2.5 Grammar ambiguities
7.3 Lexical analysis
7.3.1 General
7.3.2 Line terminators
7.3.3 Comments
7.3.4 White space
7.4 Tokens
7.4.1 General
7.4.2 Unicode character escape sequences
7.4.3 Identifiers
7.4.4 Keywords
7.4.5 Literals
7.4.5.1 General
7.4.5.2 Boolean literals
7.4.5.3 Integer literals
7.4.5.4 Real literals
7.4.5.5 Character literals
7.4.5.6 String literals
7.4.5.7 The null literal
7.4.6 Operators and punctuators
7.5 Pre-processing directives
7.5.1 General
7.5.2 Conditional compilation symbols
7.5.3 Pre-processing expressions
7.5.4 Definition directives
7.5.5 Conditional compilation directives
7.5.6 Diagnostic directives
7.5.7 Region directives
7.5.8 Line directives
7.5.9 Pragma directives
8. Basic concepts
8.1 Application startup
8.2 Application termination
8.3 Declarations
8.4 Members
8.4.1 General
8.4.2 Namespace members
8.4.3 Struct members
8.4.4 Enumeration members
8.4.5 Class members
8.4.6 Interface members
8.4.7 Array members
8.4.8 Delegate members
8.5 Member access
8.5.1 General
8.5.2 Declared accessibility
8.5.3 Accessibility domains
8.5.4 Protected access
8.5.5 Accessibility constraints
8.6 Signatures and overloading
8.7 Scopes
8.7.1 General
8.7.2 Name hiding
8.7.2.1 General
8.7.2.2 Hiding through nesting
8.7.2.3 Hiding through inheritance
8.8 Namespace and type names
8.8.1 General
8.8.2 Unqualified names
8.8.3 Fully qualified names
8.9 Automatic memory management
8.10 Execution order
9. Types
9.1 General
9.2 Reference types
9.2.1 General
9.2.2 Class types
9.2.3 The object type
9.2.4 The dynamic type
9.2.5 The string type
9.2.6 Interface types
9.2.7 Array types
9.2.8 Delegate types
9.3 Value types
9.3.1 General
9.3.2 The System.ValueType type
9.3.3 Default constructors
9.3.4 Struct types
9.3.5 Simple types
9.3.6 Integral types
9.3.7 Floating-point types
9.3.8 The decimal type
9.3.9 The bool type
9.3.10 Enumeration types
9.3.11 Nullable value types
9.3.12 Boxing and unboxing
9.4 Constructed types
9.4.1 General
9.4.2 Type arguments
9.4.3 Open and closed types
9.4.4 Bound and unbound types
9.4.5 Satisfying constraints
9.5 Type parameters
9.6 Expression tree types
9.7 The dynamic type
10. Variables
10.1 General
10.2 Variable categories
10.2.1 General
10.2.2 Static variables
10.2.3 Instance variables
10.2.3.1 General
10.2.3.2 Instance variables in classes
10.2.3.3 Instance variables in structs
10.2.4 Array elements
10.2.5 Value parameters
10.2.6 Reference parameters
10.2.7 Output parameters
10.2.8 Local variables
10.3 Default values
10.4 Definite assignment
10.4.1 General
10.4.2 Initially assigned variables
10.4.3 Initially unassigned variables
10.4.4 Precise rules for determining definite assignment
10.4.4.1 General
10.4.4.2 General rules for statements
10.4.4.3 Block statements, checked, and unchecked statements
10.4.4.4 Expression statements
10.4.4.5 Declaration statements
10.4.4.6 If statements
10.4.4.7 Switch statements
10.4.4.8 While statements
10.4.4.9 Do statements
10.4.4.10 For statements
10.4.4.11 Break, continue, and goto statements
10.4.4.12 Throw statements
10.4.4.13 Return statements
10.4.4.14 Try-catch statements
10.4.4.15 Try-finally statements
10.4.4.16 Try-catch-finally statements
10.4.4.17 Foreach statements
10.4.4.18 Using statements
10.4.4.19 Lock statements
10.4.4.20 Yield statements
10.4.4.21 General rules for constant expressions
10.4.4.22 General rules for simple expressions
10.4.4.23 General rules for expressions with embedded expressions
10.4.4.24 Invocation expressions and object creation expressions
10.4.4.25 Simple assignment expressions
10.4.4.26 && expressions
10.4.4.27 || expressions
10.4.4.28 ! expressions
10.4.4.29 ?? expressions
10.4.4.30 ?: expressions
10.4.4.31 Anonymous functions
10.5 Variable references
10.6 Atomicity of variable references
11. Conversions
11.1 General
11.2 Implicit conversions
11.2.1 General
11.2.2 Identity conversion
11.2.3 Implicit numeric conversions
11.2.4 Implicit enumeration conversions
11.2.5 Implicit nullable conversions
11.2.6 Null literal conversions
11.2.7 Implicit reference conversions
11.2.8 Boxing conversions
11.2.9 Implicit dynamic conversions
11.2.10 Implicit constant expression conversions
11.2.11 Implicit conversions involving type parameters
11.2.12 User-defined implicit conversions
11.2.13 Anonymous function conversions and method group conversions
11.3 Explicit conversions
11.3.1 General
11.3.2 Explicit numeric conversions
11.3.3 Explicit enumeration conversions
11.3.4 Explicit nullable conversions
11.3.5 Explicit reference conversions
11.3.6 Unboxing conversions
11.3.7 Explicit dynamic conversions
11.3.8 Explicit conversions involving type parameters
11.3.9 User-defined explicit conversions
11.4 Standard conversions
11.4.1 General
11.4.2 Standard implicit conversions
11.4.3 Standard explicit conversions
11.5 User-defined conversions
11.5.1 General
11.5.2 Permitted user-defined conversions
11.5.3 Evaluation of user-defined conversions
11.5.4 User-defined implicit conversions
11.5.5 User-defined explicit conversions
11.6 Conversions involving nullable types
11.6.1 Nullable Conversions
11.6.2 Lifted conversions
11.7 Anonymous function conversions
11.7.1 General
11.7.2 Evaluation of anonymous function conversions to delegate types
11.7.3 Evaluation of anonymous function conversions to expression tree types
11.8 Method group conversions
12. Expressions
12.1 General
12.2 Expression classifications
12.2.1 General
12.2.2 Values of expressions
12.3 Static and Dynamic Binding
12.3.1 General
12.3.2 Binding-time
12.3.3 Dynamic binding
12.3.4 Types of subexpressions
12.4 Operators
12.4.1 General
12.4.2 Operator precedence and associativity
12.4.3 Operator overloading
12.4.4 Unary operator overload resolution
12.4.5 Binary operator overload resolution
12.4.6 Candidate user-defined operators
12.4.7 Numeric promotions
12.4.7.1 General
12.4.7.2 Unary numeric promotions
12.4.7.3 Binary numeric promotions
12.4.8 Lifted operators
12.5 Member lookup
12.5.1 General
12.5.2 Base types
12.6 Function members
12.6.1 General
12.6.2 Argument lists
12.6.2.1 General
12.6.2.2 Corresponding parameters
12.6.2.3 Run-time evaluation of argument lists
12.6.3 Type inference
12.6.3.1 General
12.6.3.2 The first phase
12.6.3.3 The second phase
12.6.3.4 Input types
12.6.3.5 Output types
12.6.3.6 Dependence
12.6.3.7 Output type inferences
12.6.3.8 Explicit parameter type inferences
12.6.3.9 Exact inferences
12.6.3.10 Lower-bound inferences
12.6.3.11 Upper-bound inferences
12.6.3.12 Fixing
12.6.3.13 Inferred return type
12.6.3.14 Type inference for conversion of method groups
12.6.3.15 Finding the best common type of a set of expressions
12.6.4 Overload resolution
12.6.4.1 General
12.6.4.2 Applicable function member
12.6.4.3 Better function member
12.6.4.4 Better conversion from expression
12.6.4.5 Better conversion from type
12.6.4.6 Better conversion target
12.6.4.7 Overloading in generic classes
12.6.5 Compile-time checking of dynamic member invocation
12.6.6 Function member invocation
12.6.6.1 General
12.6.6.2 Invocations on boxed instances
12.7 Primary expressions
12.7.1 General
12.7.2 Literals
12.7.3 Simple names
12.7.3.1 General
12.7.3.2 Invariant meaning in blocks
12.7.4 Parenthesized expressions
12.7.5 Member access
12.7.5.1 General
12.7.5.2 Identical simple names and type names
12.7.6 Invocation expressions
12.7.6.1 General
12.7.6.2 Method invocations
12.7.6.3 Extension method invocations
12.7.6.4 Delegate invocations
12.7.7 Element access
12.7.7.1 General
12.7.7.2 Array access
12.7.7.3 Indexer access
12.7.8 This access
12.7.9 Base access
12.7.10 Postfix increment and decrement operators
12.7.11 The new operator
12.7.11.1 General
12.7.11.2 Object creation expressions
12.7.11.3 Object initializers
12.7.11.4 Collection initializers
12.7.11.5 Array creation expressions
12.7.11.6 Delegate creation expressions
12.7.11.7 Anonymous object creation expressions
12.7.12 The typeof operator
12.7.13 The sizeof operator
12.7.14 The checked and unchecked operators
12.7.15 Default value expressions
12.7.16 Anonymous method expressions
12.8 Unary operators
12.8.1 General
12.8.2 Unary plus operator
12.8.3 Unary minus operator
12.8.4 Logical negation operator
12.8.5 Bitwise complement operator
12.8.6 Prefix increment and decrement operators
12.8.7 Cast expressions
12.8.8 Await expressions
12.8.8.1 General
12.8.8.2 Awaitable expressions
12.8.8.3 Classification of await expressions
12.8.8.4 Run-time evaluation of await expressions
12.9 Arithmetic operators
12.9.1 General
12.9.2 Multiplication operator
12.9.3 Division operator
12.9.4 Remainder operator
12.9.5 Addition operator
12.9.6 Subtraction operator
12.10 Shift operators
12.11 Relational and type-testing operators
12.11.1 General
12.11.2 Integer comparison operators
12.11.3 Floating-point comparison operators
12.11.4 Decimal comparison operators
12.11.5 Boolean equality operators
12.11.6 Enumeration comparison operators
12.11.7 Reference type equality operators
12.11.8 String equality operators
12.11.9 Delegate equality operators
12.11.10 Equality operators between nullable value types and the null literal
12.11.11 The is operator
12.11.12 The as operator
12.12 Logical operators
12.12.1 General
12.12.2 Integer logical operators
12.12.3 Enumeration logical operators
12.12.4 Boolean logical operators
12.12.5 Nullable Boolean & and | operators
12.13 Conditional logical operators
12.13.1 General
12.13.2 Boolean conditional logical operators
12.13.3 User-defined conditional logical operators
12.14 The null coalescing operator
12.15 Conditional operator
12.16 Anonymous function expressions
12.16.1 General
12.16.2 Anonymous function signatures
12.16.3 Anonymous function bodies
12.16.4 Overload resolution
12.16.5 Anonymous functions and dynamic binding
12.16.6 Outer variables
12.16.6.1 General
12.16.6.2 Captured outer variables
12.16.6.3 Instantiation of local variables
12.16.7 Evaluation of anonymous function expressions
12.16.8 Implementation Exmple
12.17 Query expressions
12.17.1 General
12.17.2 Ambiguities in query expressions
12.17.3 Query expression translation
12.17.3.1 General
12.17.3.2 select and group … by clauses with continuations
12.17.3.3 Explicit range variable types
12.17.3.4 Degenerate query expressions
12.17.3.5 From, let, where, join and orderby clauses
12.17.3.6 Select clauses
12.17.3.7 Group clauses
12.17.3.8 Transparent identifiers
12.17.4 The query-expression pattern
12.18 Assignment operators
12.18.1 General
12.18.2 Simple assignment
12.18.3 Compound assignment
12.18.4 Event assignment
12.19 Expression
12.20 Constant expressions
12.21 Boolean expressions
13. Statements
13.1 General
13.2 End points and reachability
13.3 Blocks
13.3.1 General
13.3.2 Statement lists
13.4 The empty statement
13.5 Labeled statements
13.6 Declaration statements
13.6.1 General
13.6.2 Local variable declarations
13.6.3 Local constant declarations
13.7 Expression statements
13.8 Selection statements
13.8.1 General
13.8.2 The if statement
13.8.3 The switch statement
13.9 Iteration statements
13.9.1 General
13.9.2 The while statement
13.9.3 The do statement
13.9.4 The for statement
13.9.5 The foreach statement
13.10 Jump statements
13.10.1 General
13.10.2 The break statement
13.10.3 The continue statement
13.10.4 The goto statement
13.10.5 The return statement
13.10.6 The throw statement
13.11 The try statement
13.12 The checked and unchecked statements
13.13 The lock statement
13.14 The using statement
13.15 The yield statement
14. Namespaces
14.1 General
14.2 Compilation units
14.3 Namespace declarations
14.4 Extern alias directives
14.5 Using directives
14.5.1 General
14.5.2 Using alias directives
14.5.3 Using namespace directives
14.6 Namespace member declarations
14.7 Type declarations
14.8 Qualified alias member
14.8.1 General
14.8.2 Uniqueness of aliases
15. Classes
15.1 General
15.2 Class declarations
15.2.1 General
15.2.2 Class modifiers
15.2.2.1 General
15.2.2.2 Abstract classes
15.2.2.3 Sealed classes
15.2.2.4 Static classes
15.2.2.4.1 General
15.2.2.4.2 Referencing static class types
15.2.3 Type parameters
15.2.4 Class base specification
15.2.4.1 General
15.2.4.2 Base classes
15.2.4.3 Interface implementations
15.2.5 Type parameter constraints
15.2.6 Class body
15.2.7 Partial declarations
15.3 Class members
15.3.1 General
15.3.2 The instance type
15.3.3 Members of constructed types
15.3.4 Inheritance
15.3.5 The new modifier
15.3.6 Access modifiers
15.3.7 Constituent types
15.3.8 Static and instance members
15.3.9 Nested types
15.3.9.1 General
15.3.9.2 Fully qualified name
15.3.9.3 Declared accessibility
15.3.9.4 Hiding
15.3.9.5 this access
15.3.9.6 Access to private and protected members of the containing type
15.3.9.7 Nested types in generic classes
15.3.10 Reserved member names
15.3.10.1 General
15.3.10.2 Member names reserved for properties
15.3.10.3 Member names reserved for events
15.3.10.4 Member names reserved for indexers
15.3.10.5 Member names reserved for finalizers
15.4 Constants
15.5 Fields
15.5.1 General
15.5.2 Static and instance fields
15.5.3 Readonly fields
15.5.3.1 General
15.5.3.2 Using static readonly fields for constants
15.5.3.3 Versioning of constants and static readonly fields
15.5.4 Volatile fields
15.5.5 Field initialization
15.5.6 Variable initializers
15.5.6.1 General
15.5.6.2 Static field initialization
15.5.6.3 Instance field initialization
15.6 Methods
15.6.1 General
15.6.2 Method parameters
15.6.2.1 General
15.6.2.2 Value parameters
15.6.2.3 Reference parameters
15.6.2.4 Output parameters
15.6.2.5 Parameter arrays
15.6.3 Static and instance methods
15.6.4 Virtual methods
15.6.5 Override methods
15.6.6 Sealed methods
15.6.7 Abstract methods
15.6.8 External methods
15.6.9 Partial methods
15.6.10 Extension methods
15.6.11 Method body
15.7 Properties
15.7.1 General
15.7.2 Static and instance properties
15.7.3 Accessors
15.7.4 Automatically implemented properties
15.7.5 Accessibility
15.7.6 Virtual, sealed, override, and abstract accessors
15.8 Events
15.8.1 General
15.8.2 Field-like events
15.8.3 Event accessors
15.8.4 Static and instance events
15.8.5 Virtual, sealed, override, and abstract accessors
15.9 Indexers
15.10 Operators
15.10.1 General
15.10.2 Unary operators
15.10.3 Binary operators
15.10.4 Conversion operators
15.11 Instance constructors
15.11.1 General
15.11.2 Constructor initializers
15.11.3 Instance variable initializers
15.11.4 Constructor execution
15.11.5 Default constructors
15.12 Static constructors
15.13 Finalizers
15.14 Iterators
15.14.1 General
15.14.2 Enumerator interfaces
15.14.3 Enumerable interfaces
15.14.4 Yield type
15.14.5 Enumerator objects
15.14.5.1 General
15.14.5.2 The MoveNext method
15.14.5.3 The Current property
15.14.5.4 The Dispose method
15.14.6 Enumerable objects
15.14.6.1 General
15.14.6.2 The GetEnumerator method
15.15 Async Functions
15.15.1 General
15.15.2 Evaluation of a task-returning async function
15.15.3 Evaluation of a void-returning async function
16. Structs
16.1 General
16.2 Struct declarations
16.2.1 General
16.2.2 Struct modifiers
16.2.3 Partial modifier
16.2.4 Struct interfaces
16.2.5 Struct body
16.3 Struct members
16.4 Class and struct differences
16.4.1 General
16.4.2 Value semantics
16.4.3 Inheritance
16.4.4 Assignment
16.4.5 Default values
16.4.6 Boxing and unboxing
16.4.7 Meaning of this
16.4.8 Field initializers
16.4.9 Constructors
16.4.10 Static constructors
16.4.11 Automatically implemented properties
17. Arrays
17.1 General
17.2 Array types
17.2.1 General
17.2.2 The System.Array type
17.2.3 Arrays and the generic collection interfaces
17.3 Array creation
17.4 Array element access
17.5 Array members
17.6 Array covariance
17.7 Array initializers
18. Interfaces
18.1 General
18.2 Interface declarations
18.2.1 General
18.2.2 Interface modifiers
18.2.3 Variant type parameter lists
18.2.3.1 General
18.2.3.2 Variance safety
18.2.3.3 Variance conversion
18.2.4 Base interfaces
18.3 Interface body
18.4 Interface members
18.4.1 General
18.4.2 Interface methods
18.4.3 Interface properties
18.4.4 Interface events
18.4.5 Interface indexers
18.4.6 Interface member access
18.5 Qualified interface member names
18.6 Interface implementations
18.6.1 General
18.6.2 Explicit interface member implementations
18.6.3 Uniqueness of implemented interfaces
18.6.4 Implementation of generic methods
18.6.5 Interface mapping
18.6.6 Interface implementation inheritance
18.6.7 Interface re-implementation
18.6.8 Abstract classes and interfaces
19. Enums
19.1 General
19.2 Enum declarations
19.3 Enum modifiers
19.4 Enum members
19.5 The System.Enum type
19.6 Enum values and operations
20. Delegates
20.1 General
20.2 Delegate declarations
20.3 Delegate members
20.4 Delegate compatibility
20.5 Delegate instantiation
20.6 Delegate invocation
21. Exceptions
21.1 General
21.2 Causes of exceptions
21.3 The System.Exception class
21.4 How exceptions are handled
21.5 Common exception classes
22. Attributes
22.1 General
22.2 Attribute classes
22.2.1 General
22.2.2 Attribute usage
22.2.3 Positional and named parameters
22.2.4 Attribute parameter types
22.3 Attribute specification
22.4 Attribute instances
22.4.1 General
22.4.2 Compilation of an attribute
22.4.3 Run-time retrieval of an attribute instance
22.5 Reserved attributes
22.5.1 General
22.5.2 The AttributeUsage attribute
22.5.3 The Conditional attribute
22.5.3.1 General
22.5.3.2 Conditional methods
22.5.3.3 Conditional attribute classes
22.5.4 The Obsolete attribute
22.5.5 Caller-info attributes
22.5.5.1 General
22.5.5.2 The CallerLineNumber attribute
22.5.5.3 The CallerFilePath attribute
22.5.5.4 The CallerMemberName attribute
22.6 Attributes for interoperation
23. Unsafe code
23.1 General
23.2 Unsafe contexts
23.3 Pointer types
23.4 Fixed and moveable variables
23.5 Pointer conversions
23.5.1 General
23.5.2 Pointer arrays
23.6 Pointers in expressions
23.6.1 General
23.6.2 Pointer indirection
23.6.3 Pointer member access
23.6.4 Pointer element access
23.6.5 The address-of operator
23.6.6 Pointer increment and decrement
23.6.7 Pointer arithmetic
23.6.8 Pointer comparison
23.6.9 The sizeof operator
23.7 The fixed statement
23.8 Fixed-size buffers
23.8.1 General
23.8.2 Fixed-size buffer declarations
23.8.3 Fixed-size buffers in expressions
23.8.4 Definite assignment checking
23.9 Stack allocation
Annex A. Grammar
A.1 General
A.2 Lexical grammar
A.2.1 Comments
A.2.2 Tokens
A.2.3 Keywords
A.2.4 Operators and punctuators
A.2.5 Pre-processing directives
A.3 Syntactic grammar
A.3.1 Basic concepts
A.3.2 Types
A.3.3 Variables
A.3.4 Expressions
A.3.5 Statements
A.3.6 Namespaces
A.3.7 Classes
A.3.8 Structs
A.3.9 Arrays
A.3.10 Interfaces
A.3.11 Enums
A.3.12 Delegates
A.3.13 Attributes
A.4 Grammar extensions for unsafe code
Annex B. Portability issues
B.1 General
B.2 Undefined behavior
B.3 Implementation-defined behavior
B.4 Unspecified behavior
B.5 Other Issues
Annex C. Standard library
C.1 General
C.2 Standard Library Types defined in ISO/IEC 23271
C.3 Standard Library Types not defined in ISO/IEC 23271:2012
Annex D. Documentation comments
D.1 General
D.2 Introduction
D.3 Recommended tags
D.3.1 General
D.3.2
D.3.3
D.3.4
D.3.5
D.3.6
D.3.7
D.3.8
D.3.9
D.3.10
D.3.11
D.3.12
D.3.13
D.3.14
D.3.15
D.3.16
D.3.17
D.3.18
D.3.19
D.4 Processing the documentation file
D.4.1 General
D.4.2 ID string format
D.4.3 ID string examples
D.5 An example
D.5.1 C# source code
D.5.2 Resulting XML
Bibliography
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Table of Contents
Introduction
1. Scope
2. Normative references
3. Terms and definitions
4. Acronyms and abbreviations
5. General description
6. Conformance
7. Lexical structure
7.1 Programs
7.2 Grammars
7.2.1 General
7.2.2 Grammar notation
7.2.3 Lexical grammar
7.2.4 Syntactic grammar
7.2.5 Grammar ambiguities
7.3 Lexical analysis
7.3.1 General
7.3.2 Line terminators
7.3.3 Comments
7.3.4 White space
7.4 Tokens
7.4.1 General
7.4.2 Unicode character escape sequences
7.4.3 Identifiers
7.4.4 Keywords
7.4.5 Literals
7.4.5.1 General
7.4.5.2 Boolean literals
7.4.5.3 Integer literals
7.4.5.4 Real literals
7.4.5.5 Character literals
7.4.5.6 String literals
7.4.5.7 The null literal
7.4.6 Operators and punctuators
7.5 Pre-processing directives
7.5.1 General
7.5.2 Conditional compilation symbols
7.5.3 Pre-processing expressions
7.5.4 Definition directives
7.5.5 Conditional compilation directives
7.5.6 Diagnostic directives
7.5.7 Region directives
7.5.8 Line directives
7.5.9 Pragma directives
8. Basic concepts
8.1 Application startup
8.2 Application termination
8.3 Declarations
8.4 Members
8.4.1 General
8.4.2 Namespace members
8.4.3 Struct members
8.4.4 Enumeration members
8.4.5 Class members
8.4.6 Interface members
8.4.7 Array members
8.4.8 Delegate members
8.5 Member access
8.5.1 General
8.5.2 Declared accessibility
8.5.3 Accessibility domains
8.5.4 Protected access
8.5.5 Accessibility constraints
8.6 Signatures and overloading
8.7 Scopes
8.7.1 General
8.7.2 Name hiding
8.7.2.1 General
8.7.2.2 Hiding through nesting
8.7.2.3 Hiding through inheritance
8.8 Namespace and type names
8.8.1 General
8.8.2 Unqualified names
8.8.3 Fully qualified names
8.9 Automatic memory management
8.10 Execution order
9. Types
9.1 General
9.2 Reference types
9.2.1 General
9.2.2 Class types
9.2.3 The object type
9.2.4 The dynamic type
9.2.5 The string type
9.2.6 Interface types
9.2.7 Array types
9.2.8 Delegate types
9.3 Value types
9.3.1 General
9.3.2 The System.ValueType type
9.3.3 Default constructors
9.3.4 Struct types
9.3.5 Simple types
9.3.6 Integral types
9.3.7 Floating-point types
9.3.8 The decimal type
9.3.9 The bool type
9.3.10 Enumeration types
9.3.11 Nullable value types
9.3.12 Boxing and unboxing
9.4 Constructed types
9.4.1 General
9.4.2 Type arguments
9.4.3 Open and closed types
9.4.4 Bound and unbound types
9.4.5 Satisfying constraints
9.5 Type parameters
9.6 Expression tree types
9.7 The dynamic type
10. Variables
10.1 General
10.2 Variable categories
10.2.1 General
10.2.2 Static variables
10.2.3 Instance variables
10.2.3.1 General
10.2.3.2 Instance variables in classes
10.2.3.3 Instance variables in structs
10.2.4 Array elements
10.2.5 Value parameters
10.2.6 Reference parameters
10.2.7 Output parameters
10.2.8 Local variables
10.3 Default values
10.4 Definite assignment
10.4.1 General
10.4.2 Initially assigned variables
10.4.3 Initially unassigned variables
10.4.4 Precise rules for determining definite assignment
10.4.4.1 General
10.4.4.2 General rules for statements
10.4.4.3 Block statements, checked, and unchecked statements
10.4.4.4 Expression statements
10.4.4.5 Declaration statements
10.4.4.6 If statements
10.4.4.7 Switch statements
10.4.4.8 While statements
10.4.4.9 Do statements
10.4.4.10 For statements
10.4.4.11 Break, continue, and goto statements
10.4.4.12 Throw statements
10.4.4.13 Return statements
10.4.4.14 Try-catch statements
10.4.4.15 Try-finally statements
10.4.4.16 Try-catch-finally statements
10.4.4.17 Foreach statements
10.4.4.18 Using statements
10.4.4.19 Lock statements
10.4.4.20 Yield statements
10.4.4.21 General rules for constant expressions
10.4.4.22 General rules for simple expressions
10.4.4.23 General rules for expressions with embedded expressions
10.4.4.24 Invocation expressions and object creation expressions
10.4.4.25 Simple assignment expressions
10.4.4.26 && expressions
10.4.4.27 || expressions
10.4.4.28 ! expressions
10.4.4.29 ?? expressions
10.4.4.30 ?: expressions
10.4.4.31 Anonymous functions
10.5 Variable references
10.6 Atomicity of variable references
11. Conversions
11.1 General
11.2 Implicit conversions
11.2.1 General
11.2.2 Identity conversion
11.2.3 Implicit numeric conversions
11.2.4 Implicit enumeration conversions
11.2.5 Implicit nullable conversions
11.2.6 Null literal conversions
11.2.7 Implicit reference conversions
11.2.8 Boxing conversions
11.2.9 Implicit dynamic conversions
11.2.10 Implicit constant expression conversions
11.2.11 Implicit conversions involving type parameters
11.2.12 User-defined implicit conversions
11.2.13 Anonymous function conversions and method group conversions
11.3 Explicit conversions
11.3.1 General
11.3.2 Explicit numeric conversions
11.3.3 Explicit enumeration conversions
11.3.4 Explicit nullable conversions
11.3.5 Explicit reference conversions
11.3.6 Unboxing conversions
11.3.7 Explicit dynamic conversions
11.3.8 Explicit conversions involving type parameters
11.3.9 User-defined explicit conversions
11.4 Standard conversions
11.4.1 General
11.4.2 Standard implicit conversions
11.4.3 Standard explicit conversions
11.5 User-defined conversions
11.5.1 General
11.5.2 Permitted user-defined conversions
11.5.3 Evaluation of user-defined conversions
11.5.4 User-defined implicit conversions
11.5.5 User-defined explicit conversions
11.6 Conversions involving nullable types
11.6.1 Nullable Conversions
11.6.2 Lifted conversions
11.7 Anonymous function conversions
11.7.1 General
11.7.2 Evaluation of anonymous function conversions to delegate types
11.7.3 Evaluation of anonymous function conversions to expression tree types
11.8 Method group conversions
12. Expressions
12.1 General
12.2 Expression classifications
12.2.1 General
12.2.2 Values of expressions
12.3 Static and Dynamic Binding
12.3.1 General
12.3.2 Binding-time
12.3.3 Dynamic binding
12.3.4 Types of subexpressions
12.4 Operators
12.4.1 General
12.4.2 Operator precedence and associativity
12.4.3 Operator overloading
12.4.4 Unary operator overload resolution
12.4.5 Binary operator overload resolution
12.4.6 Candidate user-defined operators
12.4.7 Numeric promotions
12.4.7.1 General
12.4.7.2 Unary numeric promotions
12.4.7.3 Binary numeric promotions
12.4.8 Lifted operators
12.5 Member lookup
12.5.1 General
12.5.2 Base types
12.6 Function members
12.6.1 General
12.6.2 Argument lists
12.6.2.1 General
12.6.2.2 Corresponding parameters
12.6.2.3 Run-time evaluation of argument lists
12.6.3 Type inference
12.6.3.1 General
12.6.3.2 The first phase
12.6.3.3 The second phase
12.6.3.4 Input types
12.6.3.5 Output types
12.6.3.6 Dependence
12.6.3.7 Output type inferences
12.6.3.8 Explicit parameter type inferences
12.6.3.9 Exact inferences
12.6.3.10 Lower-bound inferences
12.6.3.11 Upper-bound inferences
12.6.3.12 Fixing
12.6.3.13 Inferred return type
12.6.3.14 Type inference for conversion of method groups
12.6.3.15 Finding the best common type of a set of expressions
12.6.4 Overload resolution
12.6.4.1 General
12.6.4.2 Applicable function member
12.6.4.3 Better function member
12.6.4.4 Better conversion from expression
12.6.4.5 Better conversion from type
12.6.4.6 Better conversion target
12.6.4.7 Overloading in generic classes
12.6.5 Compile-time checking of dynamic member invocation
12.6.6 Function member invocation
12.6.6.1 General
12.6.6.2 Invocations on boxed instances
12.7 Primary expressions
12.7.1 General
12.7.2 Literals
12.7.3 Simple names
12.7.3.1 General
12.7.3.2 Invariant meaning in blocks
12.7.4 Parenthesized expressions
12.7.5 Member access
12.7.5.1 General
12.7.5.2 Identical simple names and type names
12.7.6 Invocation expressions
12.7.6.1 General
12.7.6.2 Method invocations
12.7.6.3 Extension method invocations
12.7.6.4 Delegate invocations
12.7.7 Element access
12.7.7.1 General
12.7.7.2 Array access
12.7.7.3 Indexer access
12.7.8 This access
12.7.9 Base access
12.7.10 Postfix increment and decrement operators
12.7.11 The new operator
12.7.11.1 General
12.7.11.2 Object creation expressions
12.7.11.3 Object initializers
12.7.11.4 Collection initializers
12.7.11.5 Array creation expressions
12.7.11.6 Delegate creation expressions
12.7.11.7 Anonymous object creation expressions
12.7.12 The typeof operator
12.7.13 The sizeof operator
12.7.14 The checked and unchecked operators
12.7.15 Default value expressions
12.7.16 Anonymous method expressions
12.8 Unary operators
12.8.1 General
12.8.2 Unary plus operator
12.8.3 Unary minus operator
12.8.4 Logical negation operator
12.8.5 Bitwise complement operator
12.8.6 Prefix increment and decrement operators
12.8.7 Cast expressions
12.8.8 Await expressions
12.8.8.1 General
12.8.8.2 Awaitable expressions
12.8.8.3 Classification of await expressions
12.8.8.4 Run-time evaluation of await expressions
12.9 Arithmetic operators
12.9.1 General
12.9.2 Multiplication operator
12.9.3 Division operator
12.9.4 Remainder operator
12.9.5 Addition operator
12.9.6 Subtraction operator
12.10 Shift operators
12.11 Relational and type-testing operators
12.11.1 General
12.11.2 Integer comparison operators
12.11.3 Floating-point comparison operators
12.11.4 Decimal comparison operators
12.11.5 Boolean equality operators
12.11.6 Enumeration comparison operators
12.11.7 Reference type equality operators
12.11.8 String equality operators
12.11.9 Delegate equality operators
12.11.10 Equality operators between nullable value types and the null literal
12.11.11 The is operator
12.11.12 The as operator
12.12 Logical operators
12.12.1 General
12.12.2 Integer logical operators
12.12.3 Enumeration logical operators
12.12.4 Boolean logical operators
12.12.5 Nullable Boolean & and | operators
12.13 Conditional logical operators
12.13.1 General
12.13.2 Boolean conditional logical operators
12.13.3 User-defined conditional logical operators
12.14 The null coalescing operator
12.15 Conditional operator
12.16 Anonymous function expressions
12.16.1 General
12.16.2 Anonymous function signatures
12.16.3 Anonymous function bodies
12.16.4 Overload resolution
12.16.5 Anonymous functions and dynamic binding
12.16.6 Outer variables
12.16.6.1 General
12.16.6.2 Captured outer variables
12.16.6.3 Instantiation of local variables
12.16.7 Evaluation of anonymous function expressions
12.16.8 Implementation Exmple
12.17 Query expressions
12.17.1 General
12.17.2 Ambiguities in query expressions
12.17.3 Query expression translation
12.17.3.1 General
12.17.3.2 select and group … by clauses with continuations
12.17.3.3 Explicit range variable types
12.17.3.4 Degenerate query expressions
12.17.3.5 From, let, where, join and orderby clauses
12.17.3.6 Select clauses
12.17.3.7 Group clauses
12.17.3.8 Transparent identifiers
12.17.4 The query-expression pattern
12.18 Assignment operators
12.18.1 General
12.18.2 Simple assignment
12.18.3 Compound assignment
12.18.4 Event assignment
12.19 Expression
12.20 Constant expressions
12.21 Boolean expressions
13. Statements
13.1 General
13.2 End points and reachability
13.3 Blocks
13.3.1 General
13.3.2 Statement lists
13.4 The empty statement
13.5 Labeled statements
13.6 Declaration statements
13.6.1 General
13.6.2 Local variable declarations
13.6.3 Local constant declarations
13.7 Expression statements
13.8 Selection statements
13.8.1 General
13.8.2 The if statement
13.8.3 The switch statement
13.9 Iteration statements
13.9.1 General
13.9.2 The while statement
13.9.3 The do statement
13.9.4 The for statement
13.9.5 The foreach statement
13.10 Jump statements
13.10.1 General
13.10.2 The break statement
13.10.3 The continue statement
13.10.4 The goto statement
13.10.5 The return statement
13.10.6 The throw statement
13.11 The try statement
13.12 The checked and unchecked statements
13.13 The lock statement
13.14 The using statement
13.15 The yield statement
14. Namespaces
14.1 General
14.2 Compilation units
14.3 Namespace declarations
14.4 Extern alias directives
14.5 Using directives
14.5.1 General
14.5.2 Using alias directives
14.5.3 Using namespace directives
14.6 Namespace member declarations
14.7 Type declarations
14.8 Qualified alias member
14.8.1 General
14.8.2 Uniqueness of aliases
15. Classes
15.1 General
15.2 Class declarations
15.2.1 General
15.2.2 Class modifiers
15.2.2.1 General
15.2.2.2 Abstract classes
15.2.2.3 Sealed classes
15.2.2.4 Static classes
15.2.2.4.1 General
15.2.2.4.2 Referencing static class types
15.2.3 Type parameters
15.2.4 Class base specification
15.2.4.1 General
15.2.4.2 Base classes
15.2.4.3 Interface implementations
15.2.5 Type parameter constraints
15.2.6 Class body
15.2.7 Partial declarations
15.3 Class members
15.3.1 General
15.3.2 The instance type
15.3.3 Members of constructed types
15.3.4 Inheritance
15.3.5 The new modifier
15.3.6 Access modifiers
15.3.7 Constituent types
15.3.8 Static and instance members
15.3.9 Nested types
15.3.9.1 General
15.3.9.2 Fully qualified name
15.3.9.3 Declared accessibility
15.3.9.4 Hiding
15.3.9.5 this access
15.3.9.6 Access to private and protected members of the containing type
15.3.9.7 Nested types in generic classes
15.3.10 Reserved member names
15.3.10.1 General
15.3.10.2 Member names reserved for properties
15.3.10.3 Member names reserved for events
15.3.10.4 Member names reserved for indexers
15.3.10.5 Member names reserved for finalizers
15.4 Constants
15.5 Fields
15.5.1 General
15.5.2 Static and instance fields
15.5.3 Readonly fields
15.5.3.1 General
15.5.3.2 Using static readonly fields for constants
15.5.3.3 Versioning of constants and static readonly fields
15.5.4 Volatile fields
15.5.5 Field initialization
15.5.6 Variable initializers
15.5.6.1 General
15.5.6.2 Static field initialization
15.5.6.3 Instance field initialization
15.6 Methods
15.6.1 General
15.6.2 Method parameters
15.6.2.1 General
15.6.2.2 Value parameters
15.6.2.3 Reference parameters
15.6.2.4 Output parameters
15.6.2.5 Parameter arrays
15.6.3 Static and instance methods
15.6.4 Virtual methods
15.6.5 Override methods
15.6.6 Sealed methods
15.6.7 Abstract methods
15.6.8 External methods
15.6.9 Partial methods
15.6.10 Extension methods
15.6.11 Method body
15.7 Properties
15.7.1 General
15.7.2 Static and instance properties
15.7.3 Accessors
15.7.4 Automatically implemented properties
15.7.5 Accessibility
15.7.6 Virtual, sealed, override, and abstract accessors
15.8 Events
15.8.1 General
15.8.2 Field-like events
15.8.3 Event accessors
15.8.4 Static and instance events
15.8.5 Virtual, sealed, override, and abstract accessors
15.9 Indexers
15.10 Operators
15.10.1 General
15.10.2 Unary operators
15.10.3 Binary operators
15.10.4 Conversion operators
15.11 Instance constructors
15.11.1 General
15.11.2 Constructor initializers
15.11.3 Instance variable initializers
15.11.4 Constructor execution
15.11.5 Default constructors
15.12 Static constructors
15.13 Finalizers
15.14 Iterators
15.14.1 General
15.14.2 Enumerator interfaces
15.14.3 Enumerable interfaces
15.14.4 Yield type
15.14.5 Enumerator objects
15.14.5.1 General
15.14.5.2 The MoveNext method
15.14.5.3 The Current property
15.14.5.4 The Dispose method
15.14.6 Enumerable objects
15.14.6.1 General
15.14.6.2 The GetEnumerator method
15.15 Async Functions
15.15.1 General
15.15.2 Evaluation of a task-returning async function
15.15.3 Evaluation of a void-returning async function
16. Structs
16.1 General
16.2 Struct declarations
16.2.1 General
16.2.2 Struct modifiers
16.2.3 Partial modifier
16.2.4 Struct interfaces
16.2.5 Struct body
16.3 Struct members
16.4 Class and struct differences
16.4.1 General
16.4.2 Value semantics
16.4.3 Inheritance
16.4.4 Assignment
16.4.5 Default values
16.4.6 Boxing and unboxing
16.4.7 Meaning of this
16.4.8 Field initializers
16.4.9 Constructors
16.4.10 Static constructors
16.4.11 Automatically implemented properties
17. Arrays
17.1 General
17.2 Array types
17.2.1 General
17.2.2 The System.Array type
17.2.3 Arrays and the generic collection interfaces
17.3 Array creation
17.4 Array element access
17.5 Array members
17.6 Array covariance
17.7 Array initializers
18. Interfaces
18.1 General
18.2 Interface declarations
18.2.1 General
18.2.2 Interface modifiers
18.2.3 Variant type parameter lists
18.2.3.1 General
18.2.3.2 Variance safety
18.2.3.3 Variance conversion
18.2.4 Base interfaces
18.3 Interface body
18.4 Interface members
18.4.1 General
18.4.2 Interface methods
18.4.3 Interface properties
18.4.4 Interface events
18.4.5 Interface indexers
18.4.6 Interface member access
18.5 Qualified interface member names
18.6 Interface implementations
18.6.1 General
18.6.2 Explicit interface member implementations
18.6.3 Uniqueness of implemented interfaces
18.6.4 Implementation of generic methods
18.6.5 Interface mapping
18.6.6 Interface implementation inheritance
18.6.7 Interface re-implementation
18.6.8 Abstract classes and interfaces
19. Enums
19.1 General
19.2 Enum declarations
19.3 Enum modifiers
19.4 Enum members
19.5 The System.Enum type
19.6 Enum values and operations
20. Delegates
20.1 General
20.2 Delegate declarations
20.3 Delegate members
20.4 Delegate compatibility
20.5 Delegate instantiation
20.6 Delegate invocation
21. Exceptions
21.1 General
21.2 Causes of exceptions
21.3 The System.Exception class
21.4 How exceptions are handled
21.5 Common exception classes
22. Attributes
22.1 General
22.2 Attribute classes
22.2.1 General
22.2.2 Attribute usage
22.2.3 Positional and named parameters
22.2.4 Attribute parameter types
22.3 Attribute specification
22.4 Attribute instances
22.4.1 General
22.4.2 Compilation of an attribute
22.4.3 Run-time retrieval of an attribute instance
22.5 Reserved attributes
22.5.1 General
22.5.2 The AttributeUsage attribute
22.5.3 The Conditional attribute
22.5.3.1 General
22.5.3.2 Conditional methods
22.5.3.3 Conditional attribute classes
22.5.4 The Obsolete attribute
22.5.5 Caller-info attributes
22.5.5.1 General
22.5.5.2 The CallerLineNumber attribute
22.5.5.3 The CallerFilePath attribute
22.5.5.4 The CallerMemberName attribute
22.6 Attributes for interoperation
23. Unsafe code
23.1 General
23.2 Unsafe contexts
23.3 Pointer types
23.4 Fixed and moveable variables
23.5 Pointer conversions
23.5.1 General
23.5.2 Pointer arrays
23.6 Pointers in expressions
23.6.1 General
23.6.2 Pointer indirection
23.6.3 Pointer member access
23.6.4 Pointer element access
23.6.5 The address-of operator
23.6.6 Pointer increment and decrement
23.6.7 Pointer arithmetic
23.6.8 Pointer comparison
23.6.9 The sizeof operator
23.7 The fixed statement
23.8 Fixed-size buffers
23.8.1 General
23.8.2 Fixed-size buffer declarations
23.8.3 Fixed-size buffers in expressions
23.8.4 Definite assignment checking
23.9 Stack allocation
Annex A. Grammar
A.1 General
A.2 Lexical grammar
A.2.1 Comments
A.2.2 Tokens
A.2.3 Keywords
A.2.4 Operators and punctuators
A.2.5 Pre-processing directives
A.3 Syntactic grammar
A.3.1 Basic concepts
A.3.2 Types
A.3.3 Variables
A.3.4 Expressions
A.3.5 Statements
A.3.6 Namespaces
A.3.7 Classes
A.3.8 Structs
A.3.9 Arrays
A.3.10 Interfaces
A.3.11 Enums
A.3.12 Delegates
A.3.13 Attributes
A.4 Grammar extensions for unsafe code
Annex B. Portability issues
B.1 General
B.2 Undefined behavior
B.3 Implementation-defined behavior
B.4 Unspecified behavior
B.5 Other Issues
Annex C. Standard library
C.1 General
C.2 Standard Library Types defined in ISO/IEC 23271
C.3 Standard Library Types not defined in ISO/IEC 23271:2012
Annex D. Documentation comments
D.1 General
D.2 Introduction
D.3 Recommended tags
D.3.1 General
D.3.2
D.3.3
D.3.4
D.3.5
D.3.6
D.3.7
D.3.8
D.3.9
D.3.10
D.3.11
D.3.12
D.3.13
D.3.14
D.3.15
D.3.16
D.3.17
D.3.18
D.3.19
D.4 Processing the documentation file
D.4.1 General
D.4.2 ID string format
D.4.3 ID string examples
D.5 An example
D.5.1 C# source code
D.5.2 Resulting XML
Bibliography
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