ECMA C# Language Specification.pdf

ECMA/TC39/TG2/2000/3

Draft S tandard ECMA-xxx

October 2000

Standardizing Information and Communication Systems

C# Language Specification

Draft 01 – October 2000

Phone: +41 22 849.60.00 - Fax: +41 22 849.60.01 - URL: http://www.ecma.ch - Internet: helpdesk@ecma.ch

Table of Contents

1. Introduction....................................................................................................................................................... 1

1.1 Getting started ............................................................................................................................................... 1

1.2 Types ............................................................................................................................................................. 2

1.2.1 Predefined types...................................................................................................................................... 4

1.2.2 Conversions ............................................................................................................................................ 6

1.2.3 Array types.............................................................................................................................................. 7

1.2.4 Type system unification .......................................................................................................................... 9

1.3 Variables and parameters............................................................................................................................... 9

1.4 Automatic memory management................................................................................................................. 13

1.5 Expressions.................................................................................................................................................. 15

1.6 Statements.................................................................................................................................................... 16

1.7 Classes ......................................................................................................................................................... 19

1.7.1 Constants............................................................................................................................................... 22

1.7.2 Fields..................................................................................................................................................... 22

1.7.3 Methods ................................................................................................................................................ 23

1.7.4 Properties .............................................................................................................................................. 24

1.7.5 Events.................................................................................................................................................... 25

1.7.6 Operators............................................................................................................................................... 26

1.7.7 Indexers................................................................................................................................................. 28

1.7.8 Instance constructors............................................................................................................................. 29

1.7.9 Destructors ............................................................................................................................................ 30

1.7.10 Static constructors............................................................................................................................... 31

1.7.11 Inheritance .......................................................................................................................................... 31

1.8 Structs .......................................................................................................................................................... 33

1.9 Interfaces ..................................................................................................................................................... 33

1.10 Delegates ................................................................................................................................................... 35

1.11 Enums ........................................................................................................................................................ 36

1.12 Namespaces and assemblies ...................................................................................................................... 37

1.13 Versioning ................................................................................................................................................. 38

1.14 Attributes ................................................................................................................................................... 41

2. Lexical structure.............................................................................................................................................. 43

2.1 Phases of translation .................................................................................................................................... 43

2.2 Grammar notation........................................................................................................................................ 43

2.3 Lexical analysis ........................................................................................................................................... 44

2.3.1 Input ...................................................................................................................................................... 44

2.3.2 Input characters..................................................................................................................................... 44

2.3.3 Line terminators .................................................................................................................................... 44

2.3.4 Comments ............................................................................................................................................. 45

2.3.5 White space........................................................................................................................................... 46

2.4 Tokens ......................................................................................................................................................... 46

2.4.1 Unicode character escape sequences..................................................................................................... 46

2.4.2 Identifiers .............................................................................................................................................. 47

2.4.3 Keywords .............................................................................................................................................. 48

2.4.4 Literals .................................................................................................................................................. 49

2.4.4.1 Boolean literals............................................................................................................................... 49

2.4.4.2 Integer literals................................................................................................................................. 49

2.4.4.3 Real literals..................................................................................................................................... 50

2.4.4.4 Character literals ............................................................................................................................ 51

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C# LANGUAGE SPECIFICATION

2.4.4.5 String literals .................................................................................................................................. 52

2.4.4.6 The null literal ................................................................................................................................ 54

2.4.5 Operators and punctuators .................................................................................................................... 54

2.5 Pre-processing directives............................................................................................................................. 54

2.5.1 Pre-processing identifiers...................................................................................................................... 54

2.5.2 Pre-processing expressions ................................................................................................................... 54

2.5.3 Pre-processing declarations .................................................................................................................. 55

2.5.4 #if, #elif, #else, #endif .......................................................................................................................... 56

2.5.5 #error and #warning.............................................................................................................................. 59

2.5.6 #region and #endregion ........................................................................................................................ 59

2.5.7 #line ...................................................................................................................................................... 59

3. Basic concepts.................................................................................................................................................. 61

3.1 Program Startup........................................................................................................................................... 61

3.2 Program Termination................................................................................................................................... 62

3.3 Declarations ................................................................................................................................................. 62

3.4 Members ...................................................................................................................................................... 64

3.4.1 Namespace members ............................................................................................................................ 64

3.4.2 Struct members ..................................................................................................................................... 65

3.4.3 Enumeration members .......................................................................................................................... 65

3.4.4 Class members ...................................................................................................................................... 65

3.4.5 Interface members................................................................................................................................. 65

3.4.6 Array members ..................................................................................................................................... 65

3.4.7 Delegate members................................................................................................................................. 66

3.5 Member access ............................................................................................................................................ 66

3.5.1 Declared accessibility ........................................................................................................................... 66

3.5.2 Accessibility domains ........................................................................................................................... 67

3.5.3 Protected access .................................................................................................................................... 69

3.5.4 Accessibility constraints ....................................................................................................................... 70

3.6 Signatures and overloading ......................................................................................................................... 70

3.7 Scopes.......................................................................................................................................................... 71

3.7.1 Name hiding.......................................................................................................................................... 73

3.7.1.1 Hiding through nesting................................................................................................................... 74

3.7.1.2 Hiding through inheritance............................................................................................................. 74

3.8 Namespace and type names ......................................................................................................................... 76

3.8.1 Fully qualified names............................................................................................................................ 77

4. Types ................................................................................................................................................................ 79

4.1 Value types .................................................................................................................................................. 79

4.1.1 Default constructors .............................................................................................................................. 80

4.1.2 Struct types ........................................................................................................................................... 81

4.1.3 Simple types.......................................................................................................................................... 81

4.1.4 Integral types......................................................................................................................................... 82

4.1.5 Floating point types .............................................................................................................................. 83

4.1.6 The decimal type................................................................................................................................... 84

4.1.7 The bool type........................................................................................................................................ 85

4.1.8 Enumeration types ................................................................................................................................ 85

4.2 Reference types ........................................................................................................................................... 85

4.2.1 Class types ............................................................................................................................................ 86

4.2.2 The object type...................................................................................................................................... 86

4.2.3 The string type ...................................................................................................................................... 86

Table of Contents

4.2.4 Interface types....................................................................................................................................... 87

4.2.5 Array types............................................................................................................................................ 87

4.2.6 Delegate types....................................................................................................................................... 87

4.3 Boxing and unboxing .................................................................................................................................. 87

4.3.1 Boxing conversions............................................................................................................................... 87

4.3.2 Unboxing conversions .......................................................................................................................... 88

5. Variables .......................................................................................................................................................... 91

5.1 Variable categories ...................................................................................................................................... 91

5.1.1 Static variables ...................................................................................................................................... 91

5.1.2 Instance variables.................................................................................................................................. 91

5.1.2.1 Instance variables in classes ........................................................................................................... 92

5.1.2.2 Instance variables in structs............................................................................................................ 92

5.1.3 Array elements ...................................................................................................................................... 92

5.1.4 Value parameters .................................................................................................................................. 92

5.1.5 Reference parameters............................................................................................................................ 92

5.1.6 Output parameters................................................................................................................................. 92

5.1.7 Local variables ...................................................................................................................................... 93

5.2 Default values .............................................................................................................................................. 93

5.3 Definite assignment ..................................................................................................................................... 94

5.3.1 Initially assigned variables.................................................................................................................... 96

5.3.2 Initially unassigned variables................................................................................................................ 96

5.4 Variable references ...................................................................................................................................... 96

6. Conversions...................................................................................................................................................... 97

6.1 Implicit conversions .................................................................................................................................... 97

6.1.1 Identity conversion ............................................................................................................................... 97

6.1.2 Implicit numeric conversions................................................................................................................ 97

6.1.3 Implicit enumeration conversions......................................................................................................... 98

6.1.4 Implicit reference conversions .............................................................................................................. 98

6.1.5 Boxing conversions............................................................................................................................... 98

6.1.6 Implicit constant expression conversions ............................................................................................. 98

6.1.7 User-defined implicit conversions ........................................................................................................ 99

6.2 Explicit conversions .................................................................................................................................... 99

6.2.1 Explicit numeric conversions................................................................................................................ 99

6.2.2 Explicit enumeration conversions....................................................................................................... 100

6.2.3 Explicit reference conversions ............................................................................................................ 100

6.2.4 Unboxing conversions ........................................................................................................................ 101

6.2.5 User-defined explicit conversions....................................................................................................... 101

6.3 Standard conversions................................................................................................................................. 101

6.3.1 Standard implicit conversions............................................................................................................. 101

6.3.2 Standard explicit conversions ............................................................................................................. 102

6.4 User-defined conversions .......................................................................................................................... 102

6.4.1 Permitted user-defined conversions .................................................................................................... 102

6.4.2 Evaluation of user-defined conversions.............................................................................................. 102

6.4.3 User-defined implicit conversions ...................................................................................................... 103

6.4.4 User-defined explicit conversions....................................................................................................... 104

7. Expressions .................................................................................................................................................... 105

7.1 Expression classifications.......................................................................................................................... 105

7.1.1 Values of expressions ......................................................................................................................... 106

7.2 Operators ................................................................................................................................................... 106

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