System.Security.Permissions.PrincipalPermission.FromXml C# (CSharp) Method

        public void FromXml(SecurityElement elem)
        {
            if (elem == null)
                throw new ArgumentNullException(nameof(elem));

            if (elem.Tag == null || !elem.Tag.Equals("Permission") && !elem.Tag.Equals("IPermission"))
                throw new ArgumentException(SR.Argument_NotAPermissionElement);

            string version = elem.Attribute("version");

            if (version == null || (version != null && !version.Equals("1")))
                throw new ArgumentException(SR.Argument_InvalidXMLBadVersion);

            if (elem.Children != null && elem.Children.Count != 0)
            {
                int numChildren = elem.Children.Count;
                int count = 0;

                _idArray = new IDRole[numChildren];
                foreach (object curr in elem.Children)
                {
                    _idArray[count++] = new IDRole((SecurityElement)curr);
                }
            }
            else
                _idArray = new IDRole[0];
        }

		public void FromXmlNull () 
		{
			PrincipalPermission p = new PrincipalPermission (PermissionState.None);
			p.FromXml (null);
		}