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The Role of the Common Language Specification (CLS)
The Common Language Specification (CLS) is a subset of the CTS. The CLS defines the minimal features a language
must support to be considered a .NET language. If a complier abides by the CLS rules, all other .NET languages can
use the resulting binaries in a uniform manner. By and large, only developers creating a new .NET language need to
engross themselves in the full details of the CLS. Nevertheless, it is enlightening to examine some of these rules
firsthand.
CLS rule: All classes ultimately derive from System.Object:
For the time being, don’t concern yourself with the exact syntax seen below. We will see the details of System.
Object later in this class.
' The top-most class in the .NET world: System.Object
Public Class Object
' Reference equality by default. Override for value semantics.
Public Overridable Function Equals(obj As Object) As Boolean
Public Shared Function Equals(objA As Object, objB As Object) _
As Boolean
' Get hash value for object. Override for efficient Hash table use.
Public Overridable Function GetHashCode() As Integer
' Runtime Type Information (RTTI) for this object.
Public Function GetType() As Type
' Override to produce state data in string format.
Public Overridable Function ToString() As String
' Override to cleanup resources (non-deterministic destruction)
Protected Overridable Sub Finalize()
End Class
Like Java, the CLS does not support multiple inheritance for class types. C++ developers take note. Like Java, the
CLS allows a class to implement multiple interfaces. It is possible for an interface to have multiple base interfaces. In
other words, multiple interface inheritance is supported. CLS rule: Every type in an assembly must specify its
visibility. Although a given language may have unique keywords, the basic visibility settings are:
The CTS defines a set of core data types, each of which has a corresponding object in the System namespace. As far
as the type system itself is concerned, a type can be from the set {class, interface, structure, enumeration,
delegate}. Since the release of .NET 2.0, all types but enumerations may be created generically.
The Common Language Specification (CLS) is a subset of the CTS. The CLS defines the minimal features a language
must support to be considered a .NET language. If a complier abides by the CLS rules, all other .NET languages can
use the resulting binaries in a uniform manner. By and large, only developers creating a new .NET language need to
engross themselves in the full details of the CLS. Nevertheless, it is enlightening to examine some of these rules
firsthand.
CLS rule: All classes ultimately derive from System.Object:
For the time being, don’t concern yourself with the exact syntax seen below. We will see the details of System.
Object later in this class.
' The top-most class in the .NET world: System.Object
Public Class Object
' Reference equality by default. Override for value semantics.
Public Overridable Function Equals(obj As Object) As Boolean
Public Shared Function Equals(objA As Object, objB As Object) _
As Boolean
' Get hash value for object. Override for efficient Hash table use.
Public Overridable Function GetHashCode() As Integer
' Runtime Type Information (RTTI) for this object.
Public Function GetType() As Type
' Override to produce state data in string format.
Public Overridable Function ToString() As String
' Override to cleanup resources (non-deterministic destruction)
Protected Overridable Sub Finalize()
End Class
Like Java, the CLS does not support multiple inheritance for class types. C++ developers take note. Like Java, the
CLS allows a class to implement multiple interfaces. It is possible for an interface to have multiple base interfaces. In
other words, multiple interface inheritance is supported. CLS rule: Every type in an assembly must specify its
visibility. Although a given language may have unique keywords, the basic visibility settings are:
- Public: visible to anyone, anywhere.
- Private: only visible to members of the defining type.
- Protected: only visible to members of the defining type or members of derived types.
- Internal: visible to any type defined within the assembly. In VB, internal visibility is defined using the
Friend keyword.
The CTS defines a set of core data types, each of which has a corresponding object in the System namespace. As far
as the type system itself is concerned, a type can be from the set {class, interface, structure, enumeration,
delegate}. Since the release of .NET 2.0, all types but enumerations may be created generically.
Copyright (c) 2008. Intertech, Inc. All Rights Reserved. This information is to be used exclusively as an
online learning aid. Any attempts to copy, reproduce, or use for training is strictly prohibited.
online learning aid. Any attempts to copy, reproduce, or use for training is strictly prohibited.
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