DnsPermission.cs

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

namespace System.Net
{
    [Serializable]
    public sealed class DnsPermission : CodeAccessPermission, IUnrestrictedPermission
    {
        private bool m_noRestriction;

        public DnsPermission(PermissionState state)
        {
            m_noRestriction = (state == PermissionState.Unrestricted);
        }

        internal DnsPermission(bool free)
        {
            m_noRestriction = free;
        }

        public bool IsUnrestricted()
        {
            return m_noRestriction;
        }

        public override IPermission Copy()
        {
            return new DnsPermission(m_noRestriction);
        }

        public override IPermission Union(IPermission target)
        {
            if (target == null)
            {
                return Copy();
            }
            DnsPermission dnsPermission = target as DnsPermission;
            if (dnsPermission == null)
            {
                throw new ArgumentException(SR.GetString("net_perm_target"), "target");
            }
            return new DnsPermission(m_noRestriction || dnsPermission.m_noRestriction);
        }

        public override IPermission Intersect(IPermission target)
        {
            if (target == null)
            {
                return null;
            }
            DnsPermission dnsPermission = target as DnsPermission;
            if (dnsPermission == null)
            {
                throw new ArgumentException(SR.GetString("net_perm_target"), "target");
            }
            if (m_noRestriction && dnsPermission.m_noRestriction)
            {
                return new DnsPermission(free: true);
            }
            return null;
        }

        public override bool IsSubsetOf(IPermission target)
        {
            if (target == null)
            {
                return !m_noRestriction;
            }
            DnsPermission dnsPermission = target as DnsPermission;
            if (dnsPermission == null)
            {
                throw new ArgumentException(SR.GetString("net_perm_target"), "target");
            }
            if (m_noRestriction)
            {
                return dnsPermission.m_noRestriction;
            }
            return true;
        }

        public override void FromXml(SecurityElement securityElement)
        {
            if (securityElement == null)
            {
                throw new ArgumentNullException("securityElement");
            }
            if (!securityElement.Tag.Equals("IPermission"))
            {
                throw new ArgumentException(SR.GetString("net_no_classname"), "securityElement");
            }
            string text = securityElement.Attribute("class");
            if (text == null)
            {
                throw new ArgumentException(SR.GetString("net_no_classname"), "securityElement");
            }
            if (text.IndexOf(GetType().FullName) < 0)
            {
                throw new ArgumentException(SR.GetString("net_no_typename"), "securityElement");
            }
            string text2 = securityElement.Attribute("Unrestricted");
            m_noRestriction = (text2 != null && string.Compare(text2, "true", StringComparison.OrdinalIgnoreCase) == 0);
        }

        public override SecurityElement ToXml()
        {
            SecurityElement securityElement = new SecurityElement("IPermission");
            securityElement.AddAttribute("class", GetType().FullName + ", " + GetType().Module.Assembly.FullName.Replace('"', '\''));
            securityElement.AddAttribute("version", "1");
            if (m_noRestriction)
            {
                securityElement.AddAttribute("Unrestricted", "true");
            }
            return securityElement;
        }
    }
}