Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
CodeAccessPermission Class

CodeAccessPermission Class

Defines the underlying structure of all code access permissions.

System.Object
  System.Security.CodeAccessPermission
    More...

Namespace:  System.Security
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
<SecurityPermissionAttribute(SecurityAction.InheritanceDemand, ControlEvidence := True,  _
	ControlPolicy := True)> _
Public MustInherit Class CodeAccessPermission _
	Implements IPermission, ISecurityEncodable, IStackWalk

The CodeAccessPermission type exposes the following members.

  NameDescription
Protected methodCodeAccessPermissionInitializes a new instance of the CodeAccessPermission class.
Top

  NameDescription
Public methodAssertDeclares that the calling code can access the resource protected by a permission demand through the code that calls this method, even if callers higher in the stack have not been granted permission to access the resource. Using Assert can create security issues.
Public methodCopyWhen implemented by a derived class, creates and returns an identical copy of the current permission object.
Public methodDemandForces a SecurityException at run time if all callers higher in the call stack have not been granted the permission specified by the current instance.
Public methodDeny Obsolete. Prevents callers higher in the call stack from using the code that calls this method to access the resource specified by the current instance.
Public methodEqualsDetermines whether the specified CodeAccessPermission object is equal to the current CodeAccessPermission. (Overrides Object.Equals(Object).)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodFromXmlWhen overridden in a derived class, reconstructs a security object with a specified state from an XML encoding.
Public methodGetHashCodeGets a hash code for the CodeAccessPermission object that is suitable for use in hashing algorithms and data structures such as a hash table. (Overrides Object.GetHashCode.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIntersectWhen implemented by a derived class, creates and returns a permission that is the intersection of the current permission and the specified permission.
Public methodIsSubsetOfWhen implemented by a derived class, determines whether the current permission is a subset of the specified permission.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodPermitOnlyPrevents callers higher in the call stack from using the code that calls this method to access all resources except for the resource specified by the current instance.
Public methodStatic memberRevertAllCauses all previous overrides for the current frame to be removed and no longer in effect.
Public methodStatic memberRevertAssertCauses any previous Assert for the current frame to be removed and no longer in effect.
Public methodStatic memberRevertDeny Obsolete. Causes any previous Deny for the current frame to be removed and no longer in effect.
Public methodStatic memberRevertPermitOnlyCauses any previous PermitOnly for the current frame to be removed and no longer in effect.
Public methodToStringCreates and returns a string representation of the current permission object. (Overrides Object.ToString.)
Public methodToXmlWhen overridden in a derived class, creates an XML encoding of the security object and its current state.
Public methodUnionWhen overridden in a derived class, creates a permission that is the union of the current permission and the specified permission.
Top

Code access permissions use a stack walk to ensure that all callers of the code have been granted a permission. If a permission object is Nothing, it is handled the same as a permission object with the state PermissionState.None.

The call stack is typically represented as growing down, so that methods higher in the call stack call methods lower in the call stack.

Inheritors of the CodeAccessPermission class must be granted full trust to function correctly as permissions extending the security infrastructure. To determine that the inheritors are fully trusted, CodeAccessPermission issues an InheritanceDemand for ControlEvidence = true and ControlPolicy = true.

Notes to Inheritors

When you inherit from CodeAccessPermission, you must also implement the IUnrestrictedPermission interface.

The following CodeAccessPermission members must be overridden: Copy, Intersect, IsSubsetOf, ToXml, FromXml, and Union.

You must also define a constructor that takes a PermissionState as its only parameter.

You must apply the SerializableAttribute attribute to a class that inherits from CodeAccessPermission.

The following code example shows a permission derived from the CodeAccessPermission class.

' This custom permission is intended only for the purposes of illustration. 
' The following code shows how to create a custom permission that inherits 
' from CodeAccessPermission. The code implements all required overrides. 
' A wildcard character ('*') is implemented for the Name property. 
Imports System
Imports System.Security
Imports System.Security.Permissions
Imports System.IO
Imports System.Security.Policy
Imports System.Collections
Imports Microsoft.VisualBasic

<assembly: System.Reflection.AssemblyKeyFile("Key.snk")>

<assembly: System.Security.AllowPartiallyTrustedCallersAttribute()>
Namespace MyPermission

    <Serializable()> _
                   Public NotInheritable Class NameIdPermission
        Inherits CodeAccessPermission
        Implements IUnrestrictedPermission
        Private m_Name As String 
        Private m_Unrestricted As Boolean 


        Public Sub New(ByVal name As String)
            m_name = name
        End Sub 'New 


        Public Sub New(ByVal state As PermissionState)
            If state = PermissionState.None Then
                m_name = "" 
            ElseIf state = PermissionState.Unrestricted Then 
                Throw New ArgumentException("Unrestricted state is not allowed for identity permissions.")
            Else 
                Throw New ArgumentException("Invalid permission state.")
            End If 
        End Sub 'New  

        Public Property Name() As String 
            Get 
                Return m_name
            End Get 
            Set(ByVal Value As String)
                m_name = Value
            End Set 
        End Property 

        Public Overrides Function Copy() As IPermission
            Dim name As String
            name = m_name
            Return New NameIdPermission(name)
        End Function 'Copy

        Public Function IsUnrestricted() As Boolean Implements IUnrestrictedPermission.IsUnrestricted
            ' Always false, unrestricted state is not allowed. 
            Return m_Unrestricted
        End Function 
        Private Function VerifyType(ByVal target As IPermission) As Boolean 
            Return TypeOf target Is NameIdPermission
        End Function 'VerifyType

        Public Overrides Function IsSubsetOf(ByVal target As IPermission) As Boolean

#If (Debug) Then

            Console.WriteLine("************* Entering IsSubsetOf *********************")
#End If 
            If target Is Nothing Then
                Console.WriteLine("IsSubsetOf: target == null")
                Return False 
            End If
#If (Debug) Then
            Console.WriteLine(("This is = " + CType(Me, NameIdPermission).Name))
            Console.WriteLine(("Target is " + CType(target, NameIdPermission).m_name))
#End If 
            Try 
                Dim operand As NameIdPermission = CType(target, NameIdPermission)

                ' The following check for unrestricted permission is only included as an example for 
                ' permissions that allow the unrestricted state. It is of no value for this permission. 
                If True = operand.m_Unrestricted Then 
                    Return True 
                ElseIf True = Me.m_Unrestricted Then 
                    Return False 
                End If 

                If Not (Me.m_name Is Nothing) Then 
                    If operand.m_name Is Nothing Then 
                        Return False 
                    End If 
                    If Me.m_name = "" Then 
                        Return True 
                    End If 
                End If 
                If Me.m_name.Equals(operand.m_name) Then 
                    Return True 
                Else 
                    ' Check for wild card character '*'. 
                    Dim i As Integer = operand.m_name.LastIndexOf("*")

                    If i > 0 Then 
                        Dim prefix As String = operand.m_name.Substring(0, i)

                        If Me.m_name.StartsWith(prefix) Then 
                            Return True 
                        End If 
                    End If 
                End If 

                Return False 
            Catch 
                Throw New ArgumentException(String.Format("Argument_WrongType", Me.GetType().FullName))
            End Try 
        End Function 

        Public Overrides Function Intersect(ByVal target As IPermission) As IPermission
            Console.WriteLine("************* Entering Intersect *********************")
            If target Is Nothing Then 
                Return Nothing 
            End If
#If (Debug) Then

            Console.WriteLine(("This is = " + CType(Me, NameIdPermission).Name))
            Console.WriteLine(("Target is " + CType(target, NameIdPermission).m_name))
#End If 
            If Not VerifyType(target) Then 
                Throw New ArgumentException(String.Format("Argument is wrong type.", Me.GetType().FullName))
            End If 

            Dim operand As NameIdPermission = CType(target, NameIdPermission)

            If operand.IsSubsetOf(Me) Then 
                Return operand.Copy()
            ElseIf Me.IsSubsetOf(operand) Then 
                Return Me.Copy()
            Else 
                Return Nothing 
            End If 
        End Function 'Intersect

        Public Overrides Function Union(ByVal target As IPermission) As IPermission
#If (Debug) Then

            Console.WriteLine("************* Entering Union *********************")
#End If 
            If target Is Nothing Then 
                Return Me 
            End If
#If (Debug) Then
            Console.WriteLine(("This is = " + CType(Me, NameIdPermission).Name))
            Console.WriteLine(("Target is " + CType(target, NameIdPermission).m_name))
#End If 
            If Not VerifyType(target) Then 
                Throw New ArgumentException(String.Format("Argument_WrongType", Me.GetType().FullName))
            End If 

            Dim operand As NameIdPermission = CType(target, NameIdPermission)

            If operand.IsSubsetOf(Me) Then 
                Return Me.Copy()
            ElseIf Me.IsSubsetOf(operand) Then 
                Return operand.Copy()
            Else 
                Return Nothing 
            End If 
        End Function 'Union

        Public Overrides Sub FromXml(ByVal e As SecurityElement)
            ' The following code for unrestricted permission is only included as an example for 
            ' permissions that allow the unrestricted state. It is of no value for this permission. 
            Dim elUnrestricted As String = e.Attribute("Unrestricted")
            If Nothing <> elUnrestricted Then
                m_Unrestricted = Boolean.Parse(elUnrestricted)
                Return 
            End If 

            Dim elName As String = e.Attribute("Name")
            m_name = IIf(elName Is Nothing, Nothing, elName)
        End Sub 'FromXml

        Public Overrides Function ToXml() As SecurityElement
            ' Use the SecurityElement class to encode the permission to XML. 
            Dim esd As New SecurityElement("IPermission")

            Dim name As String = GetType(NameIdPermission).AssemblyQualifiedName
            esd.AddAttribute("class", name)
            esd.AddAttribute("version", "1.0")

            ' The following code for unrestricted permission is only included as an example for 
            ' permissions that allow the unrestricted state. It is of no value for this permission. 
            If m_Unrestricted Then
                esd.AddAttribute("Unrestricted", True.ToString())
            End If 
            If Not (m_Name Is Nothing) Then
                esd.AddAttribute("Name", m_Name)
            End If 
            Return esd
        End Function 'ToXml
    End Class ' NameIdPermission 
End Namespace

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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

System.Object
  System.Security.CodeAccessPermission
    System.Configuration.ConfigurationPermission
    System.Data.Common.DBDataPermission
    System.Data.OracleClient.OraclePermission
    System.Drawing.Printing.PrintingPermission
    System.Messaging.MessageQueuePermission
    System.Net.DnsPermission
    System.Net.Mail.SmtpPermission
    System.Net.NetworkInformation.NetworkInformationPermission
    System.Net.PeerToPeer.Collaboration.PeerCollaborationPermission
    System.Net.PeerToPeer.PnrpPermission
    System.Net.SocketPermission
    System.Net.WebPermission
    System.Security.Permissions.DataProtectionPermission
    System.Security.Permissions.EnvironmentPermission
    System.Security.Permissions.FileDialogPermission
    System.Security.Permissions.FileIOPermission
    System.Security.Permissions.GacIdentityPermission
    System.Security.Permissions.IsolatedStoragePermission
    System.Security.Permissions.KeyContainerPermission
    System.Security.Permissions.MediaPermission
    System.Security.Permissions.PublisherIdentityPermission
    System.Security.Permissions.ReflectionPermission
    System.Security.Permissions.RegistryPermission
    System.Security.Permissions.ResourcePermissionBase
    System.Security.Permissions.SecurityPermission
    System.Security.Permissions.SiteIdentityPermission
    System.Security.Permissions.StorePermission
    System.Security.Permissions.StrongNameIdentityPermission
    System.Security.Permissions.TypeDescriptorPermission
    System.Security.Permissions.UIPermission
    System.Security.Permissions.UrlIdentityPermission
    System.Security.Permissions.WebBrowserPermission
    System.Security.Permissions.ZoneIdentityPermission
    System.Transactions.DistributedTransactionPermission
    System.Web.AspNetHostingPermission
    System.Xaml.Permissions.XamlLoadPermission
Show:
© 2015 Microsoft