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CLSCompliantAttribute Class

Indicates whether a program element is compliant with the Common Language Specification (CLS). This class cannot be inherited.

For a list of all members of this type, see CLSCompliantAttribute Members.


[Visual Basic]
NotInheritable Public Class CLSCompliantAttribute
   Inherits Attribute
public sealed class CLSCompliantAttribute : Attribute
public __gc __sealed class CLSCompliantAttribute : public
class CLSCompliantAttribute extends Attribute

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.


You can apply the System.CSLCompliantAttribute attribute to the following program elements: assembly, module, class, struct, enum, constructor, method, property, field, event, interface, delegate, parameter, and return value. However, the notion of CLS compliance is only meaningful for assemblies, modules, types, and members of types, not parts of a member signature. Consequently, CLSCompliantAttribute is ignored when applied to parameter or return value program elements.

If no CLSCompliantAttribute is applied to a program element, then by default:

  • The assembly is not CLS-compliant.
  • The type is CLS-compliant only if its enclosing type or assembly is CLS-compliant.
  • The member of a type is CLS-compliant only if the type is CLS-compliant.

If an assembly is marked as CLS-compliant, any publicly exposed type in the assembly that is not CLS-compliant must be marked with CLSCompliantAttribute using a false argument. Similarly, if a class is marked as CLS-compliant, you must individually mark all members that are not CLS-compliant. All non-compliant members must provide corresponding CLS-compliant alternatives.

Attributes that are applied to assemblies or modules must occur after the C# using (Imports in Visual Basic) clauses and before the code.

For more information about using attributes, see Extending Metadata Using Attributes.

Note   The current Microsoft Visual Basic compiler intentionally does not generate a CLS-compliance warning, however, a future release of the compiler will issue that warning.


The following example applies a CLSCompliantAttribute to the entire assembly.

using System;

The following declaration generates a CLS-compliance warning because the type UInt32 is not specified in the CLS.

public int SetValue(UInt32 value);

If the declaration is marked with a CLSCompliantAttribute, no compiler warning or error is generated.


public int SetValue(UInt32 value);


Namespace: System

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

Assembly: Mscorlib (in Mscorlib.dll)

See Also

CLSCompliantAttribute Members | System Namespace | Attribute | What is the Common Language Specification? | Extending Metadata Using Attributes