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IPermission-Schnittstelle

  • Artikel

Definiert von Berechtigungstypen implementierte Methoden.

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Interface IPermission
    Inherits ISecurityEncodable
'Usage
Dim instance As IPermission

[ComVisibleAttribute(true)] 
public interface IPermission : ISecurityEncodable

[ComVisibleAttribute(true)] 
public interface class IPermission : ISecurityEncodable

/** @attribute ComVisibleAttribute(true) */ 
public interface IPermission extends ISecurityEncodable

ComVisibleAttribute(true) 
public interface IPermission extends ISecurityEncodable

Hinweise

Objekte für Berechtigungen in der Common Language Runtime beschreiben Sätze von Operationen, die für bestimmte Ressourcen gesichert werden können. Ein Berechtigungsobjekt beschreibt Operationen oder Zugriffe, die einer Sicherheitskontrolle unterliegen. Es stellt selbst keinen Zugriff und kein Recht auf die Durchführung von Operationen dar. Berechtigungen werden sowohl vom Anwendungscode als auch dem Sicherheitssystem von .NET Framework in folgender Weise verwendet.

  • Code fordert die Berechtigungen an, die er zur Ausführung benötigt.

  • Über die Sicherheitsrichtlinien des Systems werden dem Code Berechtigungen für die Ausführung gewährt.

  • In Code wird vorausgesetzt, dass der aufrufende Code über eine Berechtigung verfügt.

  • Der Code überschreibt den Sicherheitsstapel durch Assert, Deny oder Permit-only.

Hinweis

Wenn Sie eine neue Berechtigung schreiben, müssen Sie diese Schnittstelle in Ihrer Klasse implementieren.

Wichtig

Auf eine Berechtigung kann durch mehreren Threads zugegriffen werden. Beim Implementieren dieser Schnittstelle müssen Sie sicherstellen, dass die Methodenimplementierungen IsSubsetOf, Intersect, Union und Copy threadsicher sind.

Beispiel

In diesen Beispielen wird die Definition einer Berechtigungsklasse für die Verwendung mit der Codezugriffssicherheit veranschaulicht. Es werden alle erforderlichen Berechtigungsschnittstellen implementiert.

using System;
using System.Security;
using System.Security.Permissions;
using System.Reflection;

// Enumerated type for permission states.
[Serializable]
public enum SoundPermissionState 
{
    NoSound = 0,
    PlaySystemSounds = 1,
    PlayAnySound = 2
}

// Derive from CodeAccessPermission to gain implementations of the following
// sealed IStackWalk methods: Assert, Demand, Deny, and PermitOnly.
// Implement the following abstract IPermission methods: Copy, Intersect, and IsSubSetOf.
// Implementing the Union method of the IPermission class is optional.
// Implement the following abstract ISecurityEncodable methods: FromXml and ToXml.
// Making the class 'sealed' is optional.

public sealed class SoundPermission : CodeAccessPermission, IPermission, 
    IUnrestrictedPermission, ISecurityEncodable, ICloneable 
{
    private Boolean m_specifiedAsUnrestricted = false;
    private SoundPermissionState m_flags = SoundPermissionState.NoSound;

    // This constructor creates and initializes a permission with generic access.
    public SoundPermission(PermissionState state)
    {
        m_specifiedAsUnrestricted = (state == PermissionState.Unrestricted);
    }

    // This constructor creates and initializes a permission with specific access.        
    public SoundPermission(SoundPermissionState flags) 
    {
        if (!Enum.IsDefined(typeof(SoundPermissionState), flags))
            throw new ArgumentException
                ("flags value is not valid for the SoundPermissionState enuemrated type");
        m_specifiedAsUnrestricted = false;
        m_flags = flags;
    }

    // For debugging, return the state of this object as XML.
    public override String ToString() { return ToXml().ToString(); }

    // Private method to cast (if possible) an IPermission to the type.
    private SoundPermission VerifyTypeMatch(IPermission target) 
    {
        if (GetType() != target.GetType())
            throw new ArgumentException(String.Format("target must be of the {0} type",
                GetType().FullName));
        return (SoundPermission) target;
    }

    // This is the Private Clone helper method. 
    private SoundPermission Clone(Boolean specifiedAsUnrestricted, SoundPermissionState flags) 
    {
        SoundPermission soundPerm = (SoundPermission) Clone();
        soundPerm.m_specifiedAsUnrestricted = specifiedAsUnrestricted;
        soundPerm.m_flags = specifiedAsUnrestricted ? SoundPermissionState.PlayAnySound : m_flags;
        return soundPerm;
    }

    #region IPermission Members
    // Return a new object that contains the intersection of 'this' and 'target'.
    public override IPermission Intersect(IPermission target) 
    {
        // If 'target' is null, return null.
        if (target == null) return null;

        // Both objects must be the same type.
        SoundPermission soundPerm = VerifyTypeMatch(target);

        // If 'this' and 'target' are unrestricted, return a new unrestricted permission.
        if (m_specifiedAsUnrestricted && soundPerm.m_specifiedAsUnrestricted)
            return Clone(true, SoundPermissionState.PlayAnySound);

        // Calculate the intersected permissions. If there are none, return null.
        SoundPermissionState val = (SoundPermissionState)
            Math.Min((Int32) m_flags, (Int32) soundPerm.m_flags);
        if (val == 0) return null;

        // Return a new object with the intersected permission value.
        return Clone(false, val);
    }

    // Called by the Demand method: returns true if 'this' is a subset of 'target'.
    public override Boolean IsSubsetOf(IPermission target) 
    {
        // If 'target' is null and this permission allows nothing, return true.
        if (target == null) return m_flags == 0;

        // Both objects must be the same type.
        SoundPermission soundPerm = VerifyTypeMatch(target);

        // Return true if the permissions of 'this' is a subset of 'target'.
        return m_flags <= soundPerm.m_flags;
    }

    // Return a new object that matches 'this' object's permissions.
    public sealed override IPermission Copy() 
    {
        return (IPermission) Clone();
    }
    
    // Return a new object that contains the union of 'this' and 'target'.
    // Note: You do not have to implement this method. If you do not, the version
    // in CodeAccessPermission does this:
    //    1. If target is not null, a NotSupportedException is thrown.
    //    2. If target is null, then Copy is called and the new object is returned.
    public override IPermission Union(IPermission target) 
    {
        // If 'target' is null, then return a copy of 'this'.
        if (target == null) return Copy();

        // Both objects must be the same type.
        SoundPermission soundPerm = VerifyTypeMatch(target);

        // If 'this' or 'target' are unrestricted, return a new unrestricted permission.
        if (m_specifiedAsUnrestricted || soundPerm.m_specifiedAsUnrestricted)
            return Clone(true, SoundPermissionState.PlayAnySound);

        // Return a new object with the calculated, unioned permission value.
        return Clone(false, (SoundPermissionState)
            Math.Max((Int32) m_flags, (Int32) soundPerm.m_flags));
    }
    #endregion

    #region ISecurityEncodable Members
    // Populate the permission's fields from XML.
    public override void FromXml(SecurityElement e) 
    {
        m_specifiedAsUnrestricted = false;
        m_flags = 0;

        // If XML indicates an unrestricted permission, make this permission unrestricted.
        String s = (String) e.Attributes["Unrestricted"];
        if (s != null) 
        {
            m_specifiedAsUnrestricted = Convert.ToBoolean(s);
            if (m_specifiedAsUnrestricted)
                m_flags = SoundPermissionState.PlayAnySound;
        }

        // If XML indicates a restricted permission, parse the flags.
        if (!m_specifiedAsUnrestricted) 
        {
            s = (String) e.Attributes["Flags"];
            if (s != null) 
            {
                m_flags = (SoundPermissionState)
                Convert.ToInt32(Enum.Parse(typeof(SoundPermission), s, true));
            }
        }
    }

    // Produce XML from the permission's fields.
    public override SecurityElement ToXml() {
        // These first three lines create an element with the required format.
        SecurityElement e = new SecurityElement("IPermission");
        // Replace the double quotation marks () with single quotation marks ()
        // to remain XML compliant when the culture is not neutral.
        e.AddAttribute("class", GetType().AssemblyQualifiedName.Replace('\"', '\''));
        e.AddAttribute("version", "1");

        if (!m_specifiedAsUnrestricted)
            e.AddAttribute("Flags", Enum.Format(typeof(SoundPermission), m_flags, "G"));
        else
            e.AddAttribute("Unrestricted", "true");
        return e;
    }
    #endregion

    #region IUnrestrictedPermission Members
    // Returns true if permission is effectively unrestricted.
    public Boolean IsUnrestricted() 
    {
        // This means that the object is unrestricted at runtime.
        return m_flags == SoundPermissionState.PlayAnySound;
    }
    #endregion

    #region ICloneable Members

    // Return a copy of the permission.
    public Object Clone() { return MemberwiseClone(); }

    #endregion
}

using namespace System;
using namespace System::Security;
using namespace System::Security::Permissions;
using namespace System::Reflection;

// Enumerated type for permission states.
[Serializable]
public enum class SoundPermissionState
{
    NoSound = 0,
    PlaySystemSounds = 1,
    PlayAnySound = 2
};

// Derive from CodeAccessPermission to gain implementations of the following
// sealed IStackWalk methods: Assert, Demand, Deny, and PermitOnly.
// Implement the following abstract IPermission methods: 
// Copy, Intersect, and IsSubSetOf.
// Implementing the Union method of the IPermission class is optional.
// Implement the following abstract ISecurityEncodable methods: 
// FromXml and ToXml.
// Making the class 'sealed' is optional.

public ref class SoundPermission sealed : public CodeAccessPermission, 
    public IPermission, public IUnrestrictedPermission, 
    public ISecurityEncodable, public ICloneable
{
private:
    bool specifiedAsUnrestricted;
private:
    SoundPermissionState stateFlags;

    // This constructor creates and initializes 
    // a permission with generic access.
public:
    SoundPermission(PermissionState^ state)
    {
        specifiedAsUnrestricted = (state == PermissionState::Unrestricted);
    }

    // This constructor creates and initializes 
    // a permission with specific access.
public:
    SoundPermission(SoundPermissionState flags)
    {
        if (flags < SoundPermissionState::NoSound ||
            flags > SoundPermissionState::PlayAnySound)
        {
            throw gcnew ArgumentException("The value of \"flags\" is not" +
                " valid for the SoundPermissionState enumerated type");
        }
        stateFlags = flags;
    }

    // For debugging, return the state of this object as XML.
public:
    virtual String^ ToString() override
    {
        return ToXml()->ToString();
    }

    // Private method to cast (if possible) an IPermission to the type.
private:
    SoundPermission^ VerifyTypeMatch(IPermission^ target)
    {
        if (GetType() != target->GetType())
        {
            throw gcnew ArgumentException(String::Format(
                "The variable \"target\" must be of the {0} type",
                GetType()->FullName));
        }
        return (SoundPermission^) target;
    }

    // This is the Private Clone helper method.
private:
    SoundPermission^ Clone(bool specifiedAsUnrestricted, 
        SoundPermissionState flags)
    {
        SoundPermission^ soundPerm = (SoundPermission^) Clone();
        soundPerm->specifiedAsUnrestricted = specifiedAsUnrestricted;
        soundPerm->stateFlags = specifiedAsUnrestricted ? 
            SoundPermissionState::PlayAnySound : flags;
        return soundPerm;
    }

    #pragma region IPermission^ Members
    // Return a new object that contains the intersection 
    // of 'this' and 'target'.
public:
    virtual IPermission^ Intersect(IPermission^ target) override
    {
        // If 'target' is null, return null.
        if (target == nullptr)
        {
            return nullptr;
        }

        // Both objects must be the same type.
        SoundPermission^ soundPerm = VerifyTypeMatch(target);

        // If 'this' and 'target' are unrestricted, 
        // return a new unrestricted permission.
        if (specifiedAsUnrestricted && soundPerm->specifiedAsUnrestricted)
        {
            return Clone(true, SoundPermissionState::PlayAnySound);
        }

        // Calculate the intersected permissions. 
        // If there are none, return null.
        SoundPermissionState minimumPermission = (SoundPermissionState)
            Math::Min((int) stateFlags, (int) soundPerm->stateFlags);
        if ((int)minimumPermission == 0)
        {
            return nullptr;
        }

        // Return a new object with the intersected permission value.
        return Clone(false, minimumPermission);
    }

    // Called by the Demand method: returns true 
    // if 'this' is a subset of 'target'.
public:
    virtual bool IsSubsetOf(IPermission^ target) override
    {
        // If 'target' is null and this permission allows nothing, 
        // return true.
        if (target == nullptr)
        {
            return (int)stateFlags == 0;
        }

        // Both objects must be the same type.
        SoundPermission^ soundPerm = VerifyTypeMatch(target);

        // Return true if the permissions of 'this' 
        // is a subset of 'target'.
        return stateFlags <= soundPerm->stateFlags;
    }

    // Return a new object that matches 'this' object's permissions.
public:
    virtual IPermission^ Copy () override sealed
    {
        return (IPermission^) Clone();
    }

    // Return a new object that contains the union of 'this' and 'target'.
    // Note: You do not have to implement this method. 
    // If you do not, the version
    // in CodeAccessPermission does this:
    //    1. If target is not null, a NotSupportedException is thrown.
    //    2. If target is null, then Copy is called and 
    //       the new object is returned.
public:
    virtual IPermission^ Union(IPermission^ target) override
    {
        // If 'target' is null, then return a copy of 'this'.
        if (target == nullptr)
        {
            return Copy();
        }

        // Both objects must be the same type.
        SoundPermission^ soundPerm = VerifyTypeMatch(target);

        // If 'this' or 'target' are unrestricted, 
        // return a new unrestricted permission.
        if (specifiedAsUnrestricted || soundPerm->specifiedAsUnrestricted)
        {
            return Clone(true, SoundPermissionState::PlayAnySound);
        }

        // Return a new object with the calculated, unioned permission value.
        return Clone(false, (SoundPermissionState)
            Math::Max((int) stateFlags, (int) soundPerm->stateFlags));
    }
    #pragma endregion

    #pragma region ISecurityEncodable^ Members
    // Populate the permission's fields from XML.
public:
    virtual void FromXml(SecurityElement^ element) override
    {
        specifiedAsUnrestricted = false;
        stateFlags = (SoundPermissionState)0;

        // If XML indicates an unrestricted permission, 
        // make this permission unrestricted.
        String^ attributeString = 
            (String^) element->Attributes["Unrestricted"];
        if (attributeString != nullptr)
        {
            specifiedAsUnrestricted = Convert::ToBoolean(attributeString);
            if (specifiedAsUnrestricted)
            {
                stateFlags = SoundPermissionState::PlayAnySound;
            }
        }

        // If XML indicates a restricted permission, parse the flags.
        if (!specifiedAsUnrestricted)
        {
            attributeString = (String^) element->Attributes["Flags"];
            if (attributeString != nullptr)
            {
                stateFlags = (SoundPermissionState) Convert::ToInt32(
                    Enum::Parse(SoundPermissionState::typeid, 
                    attributeString, true));
            }
        }
    }

    // Produce XML from the permission's fields.
public:
    virtual SecurityElement^ ToXml() override
    {
        // These first three lines create an element with the required format.
        SecurityElement^ element = gcnew SecurityElement("IPermission");
        // Replace the double quotation marks () 
        // with single quotation marks ()
        // to remain XML compliant when the culture is not neutral.
        element->AddAttribute("class", 
            GetType()->AssemblyQualifiedName->Replace('\"', '\''));
        element->AddAttribute("version", "1");

        if (!specifiedAsUnrestricted)
        {
            element->AddAttribute("Flags", 
                Enum::Format(SoundPermissionState::typeid, stateFlags, "G"));
        }   
        else
        {
            element->AddAttribute("Unrestricted", "true");
        }
        return element;
    }
    #pragma endregion

    #pragma region IUnrestrictedPermission^ Members
    // Returns true if permission is effectively unrestricted.
public:
    virtual bool IsUnrestricted()
    {
        // This means that the object is unrestricted at runtime.
        return stateFlags == SoundPermissionState::PlayAnySound;
    }
    #pragma endregion

    #pragma region ICloneable^ Members

    // Return a copy of the permission.
public:
    virtual Object^ Clone()
    {
        return MemberwiseClone();
    }

    #pragma endregion
};

Plattformen

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

Siehe auch

Referenz

IPermission-Member
System.Security-Namespace