AllowPartiallyTrustedCallersAttribute Class


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Allows an assembly to be called by partially trusted code. Without this declaration, only fully trusted callers are able to use the assembly. This class cannot be inherited.

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


<AttributeUsageAttribute(AttributeTargets.Assembly, AllowMultiple := False,
	Inherited := False)>
Public NotInheritable Class AllowPartiallyTrustedCallersAttribute
	Inherits Attribute


Initializes a new instance of the AllowPartiallyTrustedCallersAttribute class.


Gets or sets the default partial trust visibility for code that is marked with the AllowPartiallyTrustedCallersAttribute (APTCA) attribute.


When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)


This API supports the product infrastructure and is not intended to be used directly from your code. Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)


Returns the hash code for this instance.(Inherited from Attribute.)


Gets the Type of the current instance.(Inherited from Object.)


When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)


When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)


Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)


Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)


The .NET Framework 4 introduces new security rules that affect the behavior of the AllowPartiallyTrustedCallersAttribute attribute (see Security-Transparent Code, Level 2). In the .NET Framework 4, all code defaults to security-transparent, that is, partially trusted. However, you can annotate individual types and members to assign them other transparency attributes. For this and other security changes, see Security Changes in the .NET Framework.

.NET Framework version 2.0 () assemblies must be strong-named to effectively use the AllowPartiallyTrustedCallersAttribute (APTCA) attribute. .NET Framework 4 () assemblies do not have to be strong-named for the APTCA attribute to be effective, and they can contain transparent, security-critical and security-safe-critical code. For more information about applying attributes at the assembly level, see Applying Attributes.

By default, if a strong-named, assembly does not explicitly apply this attribute at the assembly level, it can be called only by other assemblies that are granted full trust. This restriction is enforced by placing a LinkDemand for FullTrust on every public or protected method on every publicly accessible class in the assembly. Assemblies that are intended to be called by partially trusted code can declare their intent through the use of AllowPartiallyTrustedCallersAttribute. An example of the declaration in C# is [assembly:AllowPartiallyTrustedCallers]; an example in Visual Basic is <assembly:AllowPartiallyTrustedCallers>.


The presence of this assembly-level attribute prevents the default behavior of placing FullTrustLinkDemand security checks, and makes the assembly callable from any other (partially or fully trusted) assembly.

When the APTCA attribute is present, all other security checks function as intended, including any class-level or method-level declarative security attributes that are present. This attribute blocks only the implicit, fully trusted caller demand.

This is not a declarative security attribute, but a regular attribute (it derives from System.Attribute, not from System.Security.Permissions.SecurityAttribute).

For more information, see Using Libraries from Partially Trusted Code.

The following example shows how to use the AllowPartiallyTrustedCallersAttribute class.

' The following HTML code can be used to call the user control in this sample.
'	<BODY>
'		<OBJECT id="usercontrol" classid="usercontrol.dll#UserControl.UserControl1" width="800"
'		height="300" style="font-size:12;">
'		</OBJECT>
'		<p>
'	</BODY>
' To run this test control you must create a strong name key, snkey.snk, and 
' a code group that gives full trust to assemblies signed with snkey.snk.
' The user control displays an OpenFileDialog box, then displays a text box containing the name of 
' the file selected and a list box that displays the contents of the file.  The selected file must 
' contain text in order for the control to display the data properly.
' Caution  This sample demonstrates the use of the Assert method.  Calling Assert removes the 
' requirement that all code in the call chain must be granted permission to access the specified 
' resource, it can open up security vulnerabilities if used incorrectly or inappropriately. Therefore, 
' it should be used with great caution.  Assert should always be followed with a RevertAssert 
' command to restore the security settings.

Imports System
Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Data
Imports System.Windows.Forms
Imports System.IO
Imports System.Security
Imports System.Security.Permissions
Imports System.Reflection
Imports System.Runtime.CompilerServices
Imports Microsoft.VisualBasic

' This strong name key is used to create a code group that gives permissions to this assembly.

<Assembly: AssemblyKeyFile("snKey.snk")> 

<Assembly: AssemblyVersion("")> 
' The AllowPartiallyTrustedCallersAttribute requires the assembly to be signed with a strong name key.
' This attribute is necessary since the control is called by either an intranet or Internet
' Web page that should be running under restricted permissions.

<Assembly: AllowPartiallyTrustedCallers()> 

' The userControl1 displays an OpenFileDialog box, then displays a text box containing the name of 
' the file selected and a list box that displays the contents of the file.  The selected file must 
' contain text in order for the control to display the data properly.

'Demand the zone requirement for the calling application.
<ZoneIdentityPermissionAttribute(SecurityAction.Demand, Zone:=SecurityZone.Intranet)> _
Public Class UserControl1
    Inherits System.Windows.Forms.UserControl
    Private WithEvents textBox1 As System.Windows.Forms.TextBox
    Private listBox1 As System.Windows.Forms.ListBox
    ' Required designer variable.
    Private components As System.ComponentModel.Container = Nothing

    Public Sub New()
        ' This call is required by the Windows.Forms Form Designer.

        ' The OpenFileDialog box should not require any special permissions.
        Dim fileDialog As New OpenFileDialog
        If fileDialog.ShowDialog() = DialogResult.OK Then
            ' Reading the name of the selected file from the OpenFileDialog box
            ' and reading the file requires FileIOPermission.  The user control should 
            ' have this permission granted through its code group; the Web page that calls the 
            ' control should not have this permission.  The Assert command prevents a stack walk 
            ' that would fail because the caller does not have the required FileIOPermission.  
            ' The use of Assert can open up security vulnerabilities if used incorrectly or 
            ' inappropriately. Therefore, it should be used with great caution.
            ' The Assert command should be followed by a RevertAssert as soon as the file operation 
            ' is completed.
            Dim fileIOPermission As New FileIOPermission(PermissionState.Unrestricted)
            textBox1.Text = fileDialog.FileName
            ' Display the contents of the file in the text box.
            Dim fsIn As New FileStream(textBox1.Text, FileMode.Open, FileAccess.Read, FileShare.Read)
            Dim sr As New StreamReader(fsIn)

            ' Process every line in the file
            Dim Line As String
            Line = sr.ReadLine()
            While Not (Line Is Nothing)
                Line = sr.ReadLine()
            End While
            ' It is very important to call RevertAssert to restore the stack walk for
            ' file operations.
        End If
    End Sub 'NewNew

    ' Clean up any resources being used.
    Protected Overloads Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
            End If
        End If
    End Sub 'Dispose

    ' Required method for Designer support - do not modify 
    ' the contents of this method with the code editor.
    Private Sub InitializeComponent()
        Me.textBox1 = New System.Windows.Forms.TextBox
        Me.listBox1 = New System.Windows.Forms.ListBox
        ' textBox1
        Me.textBox1.Location = New System.Drawing.Point(208, 112)
        Me.textBox1.Name = "textBox1"
        Me.textBox1.Size = New System.Drawing.Size(320, 20)
        Me.textBox1.TabIndex = 0
        Me.textBox1.Text = "textBox1"
        ' listBox1
        Me.listBox1.Location = New System.Drawing.Point(200, 184)
        Me.listBox1.Name = "listBox1"
        Me.listBox1.Size = New System.Drawing.Size(336, 108)
        Me.listBox1.TabIndex = 1
        ' UserControl1
        Me.Name = "UserControl1"
        Me.Size = New System.Drawing.Size(592, 400)
    End Sub 'InitializeComponent

    Private Sub UserControl1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
    End Sub 'UserControl1_Load

    Private Sub textBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles textBox1.TextChanged
    End Sub 'textBox1_TextChanged
End Class 'UserControl1 

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 5.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1

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

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