ReadOnlyPermissionSet.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Security / ReadOnlyPermissionSet.cs / 1305376 / ReadOnlyPermissionSet.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// [....]
// 
 
using System;
using System.Collections; 
using System.Diagnostics.Contracts;
using System.Runtime.Serialization;

namespace System.Security 
{
    ///  
    ///     Read only permission sets are created from explicit XML and cannot be modified after creation time. 
    ///     This allows us to round trip the permission set to the same XML that it was originally created
    ///     from - which allows permission sets to be created from XML representing a permission set in a 
    ///     previous version of the framework to be deserialized on the current version while still
    ///     serializing back to XML that makes sense on the original framework version.
    ///
    ///     Note that while we protect against modifications of the permission set itself (such as adding or 
    ///     removing permissions), we do not make any attempt to guard against modification to the permissions
    ///     which are members of the set.  Permission accesor APIs always return a copy of the permission in 
    ///     question, although it may be mutable depending upon the permission class.  If it is mutable, users 
    ///     will only be modifing a copy of the permission, and not modifying the state of the
    ///     ReadOnlyPermissionSet. 
    /// 
    [Serializable]
    public sealed class ReadOnlyPermissionSet : PermissionSet
    { 
        private SecurityElement m_originXml;
 
        [NonSerialized] 
        private bool m_deserializing;
 
        public ReadOnlyPermissionSet(SecurityElement permissionSetXml)
        {
            if (permissionSetXml == null)
                throw new ArgumentNullException("permissionSetXml"); 

            m_originXml = permissionSetXml.Copy(); 
            base.FromXml(m_originXml); 
        }
 
        [OnDeserializing]
        private void OnDeserializing(StreamingContext ctx)
        {
            m_deserializing = true; 
        }
 
        [OnDeserialized] 
        private void OnDeserialized(StreamingContext ctx)
        { 
            m_deserializing = false;
        }

        public override bool IsReadOnly 
        {
            get { return true; } 
        } 

        public override PermissionSet Copy() 
        {
            return new ReadOnlyPermissionSet(m_originXml);
        }
 
        public override SecurityElement ToXml()
        { 
            return m_originXml.Copy(); 
        }
 
        //
        // Permission access methods - since modification to a permission would result in modifying the
        // underlying permission set, we always ensure that a copy of the permission is returned rather than
        // the permission itself. 
        //
 
        protected override IEnumerator GetEnumeratorImpl() 
        {
            return new ReadOnlyPermissionSetEnumerator(base.GetEnumeratorImpl()); 
        }

        protected override IPermission GetPermissionImpl(Type permClass)
        { 
            IPermission permission = base.GetPermissionImpl(permClass);
            return permission != null ? permission.Copy() : null; 
        } 

        // 
        // Permission set mutation methods - all of these simply reject the attempt to modify the permission
        // set by throwing an InvalidOperationException
        //
 
        protected override IPermission AddPermissionImpl(IPermission perm)
        { 
            throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_ModifyROPermSet")); 
        }
 
        public override void FromXml(SecurityElement et)
        {
            // PermissionSet uses FromXml when it deserializes itself - so if we're deserializing, let
            // the base type recreate its state, otherwise it is invalid to modify a read only permission set 
            // with a FromXml call.
            if (m_deserializing) 
            { 
                base.FromXml(et);
            } 
            else
            {
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_ModifyROPermSet"));
            } 
        }
 
        protected override IPermission RemovePermissionImpl(Type permClass) 
        {
            throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_ModifyROPermSet")); 
        }

        protected override IPermission SetPermissionImpl(IPermission perm)
        { 
            throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_ModifyROPermSet"));
        } 
    } 

    ///  
    ///     Class to enumerate permissions of a read only permission set - returning only copies of the
    ///     permissions in the underlying permission set.
    /// 
    internal sealed class ReadOnlyPermissionSetEnumerator : IEnumerator 
    {
        private IEnumerator m_permissionSetEnumerator; 
 
        internal ReadOnlyPermissionSetEnumerator(IEnumerator permissionSetEnumerator)
        { 
            Contract.Assert(permissionSetEnumerator != null);
            m_permissionSetEnumerator = permissionSetEnumerator;
        }
 
        public object Current
        { 
            get 
            {
                IPermission currentPermission = m_permissionSetEnumerator.Current as IPermission; 
                return currentPermission != null ? currentPermission.Copy() : null;
            }
        }
 
        public bool MoveNext()
        { 
            return m_permissionSetEnumerator.MoveNext(); 
        }
 
        public void Reset()
        {
            m_permissionSetEnumerator.Reset();
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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ReadOnlyPermissionSet.cs source code in C# .NET

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