How to implement a ConfigurationSection with a ConfigurationElementCollection

Question

I am trying to implement a custom configuration section in a project and I keep running up against exceptions that I do not understand  I am hoping someone can fill in the blanks here    I have App config that looks like this     lt  xml version  1 0  encoding  utf-8    gt   lt configuration gt       lt configSections gt           lt section name  ServicesSection  type  RT Core Config ServicesConfigurationSectionHandler  RT Core   gt       lt  configSections gt       lt ServicesSection type  RT Core Config ServicesSection  RT Core  gt               lt Services gt                   lt AddService Port  6996  ReportType  File    gt                   lt AddService Port  7001  ReportType  Other    gt               lt  Services gt           lt  ServicesSection gt   lt  configuration gt    I have a ServiceConfig element defined like so    public class ServiceConfig   ConfigurationElement         public ServiceConfig           public ServiceConfig int port  string reportType              Port   port        ReportType   reportType              ConfigurationProperty  Port   DefaultValue   0  IsRequired   true  IsKey   true       public int Port              get   return  int  this  Port            set   this  Port     value                ConfigurationProperty  ReportType   DefaultValue    File   IsRequired   true  IsKey   false       public string ReportType             get   return  string  this  ReportType            set   this  ReportType     value                And I have a ServiceCollection defined like so    public class ServiceCollection   ConfigurationElementCollection         public ServiceCollection               Console WriteLine  ServiceCollection Constructor               public ServiceConfig this int index              get   return  ServiceConfig BaseGet index           set                 if  BaseGet index     null                      BaseRemoveAt index                     BaseAdd index  value                      public void Add ServiceConfig serviceConfig              BaseAdd serviceConfig              public void Clear               BaseClear               protected override ConfigurationElement CreateNewElement               return new ServiceConfig               protected override object GetElementKey ConfigurationElement element              return   ServiceConfig  element  Port             public void Remove ServiceConfig serviceConfig              BaseRemove serviceConfig Port              public void RemoveAt int index              BaseRemoveAt index              public void Remove string name              BaseRemove name               The part I am missing is what to do for the handler  Originally  I tried to implement an IConfigurationSectionHandler but found two things    it didn t work it s deprecated     I m completely lost now on what to do so I can read my data from config  Any help please

User · Answer

Try inheriting from ConfigurationSection. This blog post by Phil Haack has an example.

Confirmed, per the documentation for IConfigurationSectionHandler:

In .NET Framework version 2.0 and above, you must instead derive from the ConfigurationSection class to implement the related configuration section handler.

User · Answer

This is generic code for configuration collection    public class GenericConfigurationElementCollection lt T gt      ConfigurationElementCollection  IEnumerable lt T gt  where T   ConfigurationElement  new         List lt T gt   elements   new List lt T gt          protected override ConfigurationElement CreateNewElement                 T newElement   new T             elements Add newElement           return newElement             protected override object GetElementKey ConfigurationElement element                return  elements Find e   gt  e Equals element               public new IEnumerator lt T gt  GetEnumerator                 return  elements GetEnumerator              After you have GenericConfigurationElementCollection   you can simple use it in the config section  this is an example from my Dispatcher    public class  DispatcherConfigurationSection  ConfigurationSection        ConfigurationProperty  maxRetry   IsRequired   false  DefaultValue   5       public int MaxRetry               get                       return  int this  maxRetry                      set                       this  maxRetry     value                        ConfigurationProperty  eventsDispatches   IsRequired   true        ConfigurationCollection typeof EventsDispatchConfigurationElement   AddItemName    add   ClearItemsName    clear   RemoveItemName    remove        public GenericConfigurationElementCollection lt EventsDispatchConfigurationElement gt  EventsDispatches               get   return  GenericConfigurationElementCollection lt EventsDispatchConfigurationElement gt  this  eventsDispatches                The Config Element is config Here   public class EventsDispatchConfigurationElement   ConfigurationElement        ConfigurationProperty  name   IsRequired   true       public string Name               get                       return  string  this  name                      set                       this  name     value                      The config file would look like this    lt  xml version  1 0  encoding  utf-8    gt     lt dispatcherConfigurationSection gt       lt eventsDispatches gt         lt add name  Log   gt  lt  add gt         lt add name  Notification   gt  lt  add gt         lt add name  tester   gt  lt  add gt       lt  eventsDispatches gt     lt  dispatcherConfigurationSection gt    Hope it help

User · Answer

If you are looking for a custom configuration section like following    lt CustomApplicationConfig gt           lt Credentials Username  itsme  Password  mypassword   gt           lt PrimaryAgent Address  10 5 64 26  Port  3560   gt           lt SecondaryAgent Address  10 5 64 7  Port  3570   gt           lt Site Id  123    gt           lt Lanes gt             lt Lane Id  1  PointId  north  Direction  Entry   gt             lt Lane Id  2  PointId  south  Direction  Exit   gt           lt  Lanes gt    lt  CustomApplicationConfig gt    then you can use my implementation of configuration section so to get started add System Configuration assembly reference to your project  Look at the each nested elements I used  First one is Credentials with two attributes so lets add it first  Credentials Element  public class CredentialsConfigElement   System Configuration ConfigurationElement                ConfigurationProperty  Username            public string Username                       get                                return base  Username   as string                                    ConfigurationProperty  Password            public string Password                       get                               return base  Password   as string                                  PrimaryAgent and SecondaryAgent  Both has the same attributes and seem like a Address to a set of servers for a primary and a failover  so you just need to create one element class for both of those like following   public class ServerInfoConfigElement   ConfigurationElement                ConfigurationProperty  Address            public string Address                       get                               return base  Address   as string                                    ConfigurationProperty  Port            public int  Port                       get                               return base  Port   as int                                   I ll explain how to use two different element with one class later in this post  let us skip the SiteId as there is no difference in it  You just have to create one class same as above with one property only  let us see how to implement Lanes collection  it is splitted in two parts first you have to create an element implementation class then you have to create collection element class   LaneConfigElement   public class LaneConfigElement   ConfigurationElement                ConfigurationProperty  Id            public string Id                       get                               return base  Id   as string                                    ConfigurationProperty  PointId            public string PointId                       get                               return base  PointId   as string                                    ConfigurationProperty  Direction            public Direction  Direction                       get                               return base  Direction   as Direction                                      public enum Direction                Entry          Exit         you can notice that one attribute of LanElement is an Enumeration and if you try to use any other value in configuration which is not defined in Enumeration application will throw an System Configuration ConfigurationErrorsException on startup  Ok lets move on to Collection Definition   ConfigurationCollection typeof LaneConfigElement   AddItemName    Lane   CollectionType   ConfigurationElementCollectionType BasicMap       public class LaneConfigCollection   ConfigurationElementCollection               public LaneConfigElement this int index                        get   return  LaneConfigElement BaseGet index                 set                               if  BaseGet index     null                                        BaseRemoveAt index                                     BaseAdd index  value                                    public void Add LaneConfigElement serviceConfig                        BaseAdd serviceConfig                      public void Clear                         BaseClear                       protected override ConfigurationElement CreateNewElement                         return new LaneConfigElement                       protected override object GetElementKey ConfigurationElement element                        return   LaneConfigElement element  Id                     public void Remove LaneConfigElement serviceConfig                        BaseRemove serviceConfig Id                      public void RemoveAt int index                        BaseRemoveAt index                      public void Remove String name                        BaseRemove name                      you can notice that I have set the AddItemName    Lane  you can choose whatever you like for your collection entry item  i prefer to use  add  the default one but i changed it just for the sake of this post   Now all of our nested Elements have been implemented now we should aggregate all of those in a class which has to implement System Configuration ConfigurationSection  CustomApplicationConfigSection  public class CustomApplicationConfigSection   System Configuration ConfigurationSection               private static readonly ILog log   LogManager GetLogger typeof CustomApplicationConfigSection            public const string SECTION NAME    CustomApplicationConfig             ConfigurationProperty  Credentials            public CredentialsConfigElement Credentials                       get                               return base  Credentials   as CredentialsConfigElement                                    ConfigurationProperty  PrimaryAgent            public ServerInfoConfigElement PrimaryAgent                       get                               return base  PrimaryAgent   as ServerInfoConfigElement                                    ConfigurationProperty  SecondaryAgent            public ServerInfoConfigElement SecondaryAgent                       get                               return base  SecondaryAgent   as ServerInfoConfigElement                                    ConfigurationProperty  Site            public SiteConfigElement Site                       get                               return base  Site   as SiteConfigElement                                    ConfigurationProperty  Lanes            public LaneConfigCollection Lanes                       get   return base  Lanes   as LaneConfigCollection                      Now you can see that we have two properties with name PrimaryAgent and SecondaryAgent both have the same type now you can easily understand why we had only one implementation class against these two element    Before you can use this newly invented configuration section in your app config  or web config  you just need to tell you application that you have invented your own configuration section and give it some respect  to do so you have to add following lines in app config  may be right after start of root  tag     lt configSections gt       lt section name  CustomApplicationConfig  type  MyNameSpace CustomApplicationConfigSection  MyAssemblyName    gt     lt  configSections gt    NOTE  MyAssemblyName should be without  dll e g  if you assembly file name is myDll dll then use myDll instead of myDll dll  to retrieve this configuration use following line of code any where in your application   CustomApplicationConfigSection config   System Configuration ConfigurationManager GetSection CustomApplicationConfigSection SECTION NAME  as CustomApplicationConfigSection    I hope above post would help you to get started with a bit complicated kind of custom config sections    Happy Coding         Edit     To Enable LINQ on LaneConfigCollection you have to implement IEnumerable lt LaneConfigElement gt   And Add following implementation of GetEnumerator  public new IEnumerator lt LaneConfigElement gt  GetEnumerator                         int count   base Count              for  int i   0  i  lt  count  i                                  yield return base BaseGet i  as LaneConfigElement                            for the people who are still confused about how yield really works read this nice article   Two key points taken from above article are     it doesn   t really end the method   s execution  yield return pauses the   method execution and the next time you call it  for the next   enumeration value   the method will continue to execute from the last   yield return call  It sounds a bit confusing I think     Shay Friedman       Yield is not a feature of the  Net runtime  It is just a C  language   feature which gets compiled into simple IL code by the C  compiler   Lars Corneliussen

User · Answer

The previous answer is correct but I ll give you all the code as well   Your app config should look like this    lt  xml version  1 0  encoding  utf-8    gt   lt configuration gt      lt configSections gt         lt section name  ServicesSection  type  RT Core Config ServiceConfigurationSection  RT Core   gt      lt  configSections gt      lt ServicesSection gt         lt Services gt            lt add Port  6996  ReportType  File    gt            lt add Port  7001  ReportType  Other    gt         lt  Services gt      lt  ServicesSection gt   lt  configuration gt    Your ServiceConfig and ServiceCollection classes remain unchanged   You need a new class   public class ServiceConfigurationSection   ConfigurationSection       ConfigurationProperty  Services   IsDefaultCollection   false       ConfigurationCollection typeof ServiceCollection          AddItemName    add          ClearItemsName    clear          RemoveItemName    remove       public ServiceCollection Services            get                  return  ServiceCollection base  Services                     And that should do the trick  To consume it you can use   ServiceConfigurationSection serviceConfigSection      ConfigurationManager GetSection  ServicesSection   as ServiceConfigurationSection   ServiceConfig serviceConfig   serviceConfigSection Services 0

User · Answer

An easier alternative for those who would prefer not to write all that configuration boilerplate manually     1  Install Nerdle AutoConfig from NuGet   2  Define your ServiceConfig type  either a concrete class or just an interface  either will do   public interface IServiceConfiguration       int Port   get        ReportType ReportType   get        3  You ll need a type to hold the collection  e g   public interface IServiceCollectionConfiguration       IEnumerable lt IServiceConfiguration gt  Services   get         4  Add the config section like so  note camelCase naming    lt configSections gt     lt section name  serviceCollection  type  Nerdle AutoConfig Section  Nerdle AutoConfig   gt   lt  configSections gt    lt serviceCollection gt     lt services gt       lt service port  6996  reportType  File    gt       lt service port  7001  reportType  Other    gt     lt  services gt   lt  serviceCollection gt    5  Map with AutoConfig  var services   AutoConfig Map lt IServiceCollectionConfiguration gt

[c#] How to implement a ConfigurationSection with a ConfigurationElementCollection

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