public static SecurityDeclaration Xml2PermissionSet()

in ILRepack/PermissionsetHelper.cs [98:151]
50 lines of code
18 McCabe index (conditional complexity)

        public static SecurityDeclaration Xml2PermissionSet(SecurityDeclaration xmlDeclaration, ModuleDefinition targetModule)
        {
            if (!xmlDeclaration.HasSecurityAttributes || xmlDeclaration.SecurityAttributes.Count == 0)
                // nothing to convert
                return null;
            if (xmlDeclaration.SecurityAttributes.Count > 1)
                throw new Exception("Cannot convert SecurityDeclaration with more than one attribute");

            SecurityAttribute sa = xmlDeclaration.SecurityAttributes[0];
            if (sa.HasFields)
                throw new NotSupportedException("Cannot convert SecurityDeclaration with fields");
            if (!sa.HasProperties || sa.Properties.Count > 1)
                throw new NotSupportedException("Invalid XML SecurityDeclaration (only 1 property supported)");
            CustomAttributeNamedArgument arg = sa.Properties[0];
            if (arg.Name != "XML" || arg.Argument.Type.FullName != "System.String")
                throw new ArgumentException("Property \"XML\" expected");
            if (string.IsNullOrEmpty(arg.Argument.Value as string))
                return null;
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml((string)arg.Argument.Value);
            XmlNode permissionSet = xmlDoc.SelectSingleNode("/PermissionSet");
            if (permissionSet == null)
                return null;
            XmlNode permissionSetClass = permissionSet.SelectSingleNode("@class"); // check version?
            if (permissionSetClass == null)
                return null;
            if (permissionSetClass.Value != "System.Security.PermissionSet")
                return null;
            XmlNode iPermission = permissionSet.SelectSingleNode("IPermission");
            if (iPermission == null)
                return null;
            XmlNode iPermissionClass = iPermission.SelectSingleNode("@class"); // check version?
            if (iPermissionClass == null)
                return null;

            // Create Namespace & Name from FullName, AssemblyName can be ignored since we look it up.
            string[] valueParts = iPermissionClass.Value.Split(',');
            Collection<string> classNamespace = new Collection<string>(valueParts[0].Split('.'));
            string assemblyName = valueParts[1].Trim();
            string className = classNamespace[classNamespace.Count - 1];
            classNamespace.RemoveAt(classNamespace.Count - 1);
            SecurityAttribute attribute = new SecurityAttribute(GetTypeRef(string.Join(".", classNamespace.ToArray()), className, assemblyName, targetModule));
            foreach (XmlAttribute xmlAttr in iPermission.Attributes)
            {
                if ((xmlAttr.Name != "class") && (xmlAttr.Name != "version"))
                {
                    attribute.Properties.Add(new CustomAttributeNamedArgument(xmlAttr.Name,
                        new CustomAttributeArgument(targetModule.TypeSystem.String, xmlAttr.Value)));
                }
            }
            SecurityDeclaration newSd = new SecurityDeclaration(xmlDeclaration.Action);
            newSd.SecurityAttributes.Add(attribute);
            return newSd;
        }