Visual Basic (Declaration)

<AttributeUsageAttribute(AttributeTargets.Assembly Or AttributeTargets.Module Or AttributeTargets.Class Or AttributeTargets.Struct Or AttributeTargets.Enum Or AttributeTargets.Constructor Or AttributeTargets.Method Or AttributeTargets.Property Or AttributeTargets.Field Or AttributeTargets.Event Or AttributeTargets.Interface Or AttributeTargets.Delegate, AllowMultiple := False,  _
    Inherited := False)> _
Public NotInheritable Class SecurityCriticalAttribute _
    Inherits Attribute

Visual Basic (Usage)

Dim instance As SecurityCriticalAttribute

C#

[AttributeUsageAttribute(AttributeTargets.Assembly|AttributeTargets.Module|AttributeTargets.Class|AttributeTargets.Struct|AttributeTargets.Enum|AttributeTargets.Constructor|AttributeTargets.Method|AttributeTargets.Property|AttributeTargets.Field|AttributeTargets.Event|AttributeTargets.Interface|AttributeTargets.Delegate, AllowMultiple = false, 
    Inherited = false)]
public sealed class SecurityCriticalAttribute : Attribute

Security-critical operations are actions that affect code access security, such as elevation of user rights, calling unsafe managed code, and so forth. The SecurityCriticalAttribute attribute must be applied to code for the code to perform security-critical operations. Operations that are not security-critical are described as either transparent or safe-critical. Transparent code cannot call security-critical code. However, transparent code can call types and members that are marked with the SecuritySafeCriticalAttribute attribute.

For assemblies that are installed with Silverlight, the presence of the SecurityCriticalAttribute at the assembly level identifies the entire assembly as security-critical. The SecurityCriticalAttribute is ignored when it is applied in user assemblies, that is, in assemblies that are not installed with the Silverlight library assemblies and that are not signed with a specific strong-name key.

System..::.Object
  System..::.Attribute
    System.Security..::.SecurityCriticalAttribute

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

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Reference