Equivalent to app config for a library DLL

Question

Is there an equivalent to app config for libraries  DLLs   If not  what is the easiest way to store configuration settings that are specific to a library  Please consider that the library might be used in different applications

User · Answer

If you add Settings to a Class Library project in Visual Studio (Project Properties, Settings), it will add an app.config file to your project with the relevant userSettings/applicatioNSettings sections, and the default values for these settings from your Settings.settings file.

However this configuration file will not be used at runtime - instead the class library uses the configuration file of its hosting application.

I believe the main reason for generating this file is so that you can copy/paste the settings into the host application's configuration file.

User · Answer

You can have separate configuration file  but you ll have to read it  manually   the ConfigurationManager AppSettings  key   will read only the config of the running assembly   Assuming you re using Visual Studio as your IDE  you can right click the desired project   Add   New item   Application Configuration File     This will add App config to the project folder  put your settings in there under  lt appSettings gt  section  In case you re not using Visual Studio and adding the file manually  make sure to give it such name  DllName dll config  otherwise the below code won t work properly   Now to read from this file have such function   string GetAppSetting Configuration config  string key        KeyValueConfigurationElement element   config AppSettings Settings key       if  element    null                string value   element Value          if   string IsNullOrEmpty value               return value            return string Empty      And to use it   Configuration config   null  string exeConfigPath   this GetType   Assembly Location  try       config   ConfigurationManager OpenExeConfiguration exeConfigPath     catch  Exception ex          handle errror here   means DLL has no sattelite configuration file     if  config    null        string myValue   GetAppSetting config   myKey                You ll also have to add reference to System Configuration namespace in order to have the ConfigurationManager class available   When building the project  in addition to the DLL you ll have DllName dll config file as well  that s the file you have to publish with the DLL itself   The above is basic sample code  for those interested in a full scale example  please refer to this other answer

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Configuration files are application-scoped and not assembly-scoped  So you ll need to put your library s configuration sections in every application s configuration file that is using your library   That said  it is not a good practice to get configuration from the application s configuration file  specially the appSettings section  in a class library  If your library needs parameters  they should probably be passed as method arguments in constructors  factory methods  etc  by whoever is calling your library  This prevents calling applications from accidentally reusing configuration entries that were expected by the class library   That said  XML configuration files are extremely handy  so the best compromise that I ve found is using custom configuration sections  You get to put your library s configuration in an XML file that is automatically read and parsed by the framework and you avoid potential accidents   You can learn more about custom configuration sections on MSDN and also Phil Haack has a nice article on them

User · Answer

assemblies don t have their own app config file  They use the app config file of the application that is using them  So if your assembly is expecting certain things in the config file  then just make sure your application s config file has those entries in there   If your assembly is being used by multiple applications then each of those applications will need to have those entries in their app config file   What I would recommended you do is define properties on the classes in your assembly for those values for example  private string ExternalServicesUrl     get         string externalServiceUrl   ConfigurationManager AppSettings  ExternalServicesUrl        if  String IsNullOrEmpty externalServiceUrl         throw new MissingConfigFileAppSettings  The Config file is missing the appSettings entry for  ExternalServicesUrl        return externalServiceUrl          Here  the property ExternalServicesUrl get s its value from the application s config file  If any application using this assembly is missing that setting in the config file you ll get an exception o it s clear that something went missing   MissingConfigFileAppSettings is a custom Exception  You may want to throw a different exception   Of course a better design would be for the method of those classes to be provided those values as parameters rather than relying on config file setting  That way the applications using these classes can decide from where and how they provide these values

User · Answer

Unfortunately  you can only have one app config file per executable  so if you have DLL   s linked into your application  they cannot have their own app config files    Solution is   You don t need to put the App config file in the Class Library s project  You put the App config file in the application that is referencing your class  library s dll   For example  let s say we have a class library named MyClasses dll which  uses the app config file like so   string connect    ConfigurationSettings AppSettings  MyClasses ConnectionString      Now  let s say we have an Windows Application named MyApp exe which  references MyClasses dll   It would contain an App config with an entry such  as    lt appSettings gt       lt add key  MyClasses ConnectionString           value  Connection string body goes here    gt   lt  appSettings gt    OR  An xml file is best equivalent for app config  Use xml serialize deserialize as needed   You can call it what every you want   If your config is  static  and does not need to change  your could also add it to the project as an embedded resource   Hope it gives some Idea

User · Answer

As far as I m aware  you have to copy   paste the sections you want from the library  config into the applications  config file   You only get 1 app config per executable instance

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Preamble  I m using NET 2 0   The solution posted by Yiannis Leoussis is acceptable but I had some problem with it   First  the static AppSettingsSection AppSettings    AppSettingsSection myDllConfig GetSection  appSettings    returns null  I had to change it to static AppSettingSection   myDllConfig AppSettings   Then the return  T Convert ChangeType AppSettings Settings name  Value  typeof T   nfi   doesn t have a catch for Exceptions  So I ve changed it  try       return  T Convert ChangeType AppSettings Settings name  Value  typeof T   nfi     catch  Exception ex        return default T       This works very well but if you have a different dll you have to rewrite every time the code for every assembly  So  this is my version for an Class to instantiate every time you need   public class Settings       private AppSettingsSection  appSettings      private NumberFormatInfo  nfi       public Settings Assembly currentAssembly                UriBuilder uri   new UriBuilder currentAssembly CodeBase           string configPath   Uri UnescapeDataString uri Path           Configuration myDllConfig   ConfigurationManager OpenExeConfiguration configPath            appSettings   myDllConfig AppSettings           nfi   new NumberFormatInfo                           NumberGroupSeparator                    CurrencyDecimalSeparator                               public T Setting lt T gt  string name                try                       return  T Convert ChangeType  appSettings Settings name  Value  typeof T    nfi                     catch  Exception ex                        return default T                       For a config    lt add key  Enabled  value  true    gt   lt add key  ExportPath  value  c      gt   lt add key  Seconds  value  25    gt   lt add key  Ratio  value  0 14    gt    Use it as   Settings  setting   new Settings Assembly GetExecutingAssembly      somebooleanvar    settings Setting lt bool gt   Enabled    somestringlvar    settings Setting lt string gt   ExportPath    someintvar        settings Setting lt int gt   Seconds    somedoublevar     settings Setting lt double gt   Ratio

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I faced the same problem and resolved it by creating a static class Parameters after adding an Application Configuration File to the project   public static class Parameters          For a Web Application     public static string PathConfig   get  private set              Path Combine AppDomain CurrentDomain BaseDirectory   web config            For a Class Library     public static string PathConfig   get  private set              Path Combine AppDomain CurrentDomain BaseDirectory   bin    LibraryName dll config         public static string GetParameter string paramName                string paramValue   string Empty           using  Stream stream   File OpenRead PathConfig                         XDocument xdoc   XDocument Load stream                XElement element   xdoc Element  configuration   Element  appSettings   Elements   First a   gt  a Attribute  key   Value    paramName               paramValue   element Attribute  value   Value                     return paramValue            Then get a parameter like this   Parameters GetParameter  keyName

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I am currently creating plugins for a retail software brand  which are actually   net class libraries  As a requirement  each plugin needs to be configured using a config file  After a bit of research and testing  I compiled the following class  It does the job flawlessly  Note that I haven t implemented local exception handling in my case because  I catch exceptions at a higher level   Some tweaking maybe needed to get the decimal point right  in case of decimals and doubles  but it works fine for my CultureInfo     static class Settings       static UriBuilder uri   new UriBuilder Assembly GetExecutingAssembly   CodeBase       static Configuration myDllConfig   ConfigurationManager OpenExeConfiguration uri Path       static AppSettingsSection AppSettings    AppSettingsSection myDllConfig GetSection  appSettings        static NumberFormatInfo nfi   new NumberFormatInfo                   NumberGroupSeparator                CurrencyDecimalSeparator                    public static T Setting lt T gt  string name                return  T Convert ChangeType AppSettings Settings name  Value  typeof T   nfi             App Config file sample   lt add key  Enabled  value  true    gt   lt add key  ExportPath  value  c      gt   lt add key  Seconds  value  25    gt   lt add key  Ratio  value  0 14    gt    Usage     somebooleanvar   Settings Setting lt bool gt   Enabled      somestringlvar   Settings Setting lt string gt   ExportPath      someintvar       Settings Setting lt int gt   Seconds      somedoublevar    Settings Setting lt double gt   Ratio      Credits to Shadow Wizard  amp  MattC

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I took a look at the AppDomain instead of the assembly  This has the benefit of working inside static methods of a library  Link seems to work great for getting the key value as suggested by the other answers here  public class DLLConfig       public static string GetSettingByKey AppDomain currentDomain  string configName  string key                string value   string Empty          try                         string exeConfigPath    currentDomain RelativeSearchPath    currentDomain BaseDirectory     quot    quot    configName              if  File Exists exeConfigPath                                 using  Stream stream   File OpenRead exeConfigPath                                         XDocument xdoc   XDocument Load stream                       XElement element   xdoc Element  quot configuration quot   Element  quot appSettings quot   Elements   First a   gt  a Attribute  quot key quot   Value    key                       value   element Attribute  quot value quot   Value                                                     catch  Exception ex                                               return value                        Use it within your library class like so  namespace ProjectName        public class ClassName                 public static string SomeStaticMethod                           string value   DLLConfig GetSettingByKey AppDomain CurrentDomain  quot ProjectName dll config quot    quot keyname quot

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use from configurations must be very very easy like this    var config   new MiniConfig  setting conf     config AddOrUpdate  port    1580     if  config TryGet  port   out int port      if config exist       Console Write port       for more details see MiniConfig

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In response to the original question  I typically add the config file in my test project as a link  you can then use the DeploymentItem attribute to addit to the Out folder of the test run    TestClass   DeploymentItem  MyProject Cache dll config    public class CacheTest                               In response to the comments that Assemblies can t be project specific  they can and it provides great flexibility esp  when working with IOC frameworks

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public class ConfigMan        region Members      string  assemblyLocation      Configuration  configuration        endregion Members       region Constructors           lt summary gt          Loads config file settings for libraries that use assembly dll config files          lt  summary gt           lt param name  assemblyLocation  gt The full path or UNC location of the loaded file that contains the manifest  lt  param gt      public ConfigMan string assemblyLocation                 assemblyLocation   assemblyLocation              endregion Constructors       region Properties      Configuration Configuration               get                       if   configuration    null                                try                                        configuration   ConfigurationManager OpenExeConfiguration  assemblyLocation                                     catch  Exception exception                                                                return  configuration                        endregion Properties       region Methods      public string GetAppSetting string key                string result   string Empty          if  Configuration    null                        KeyValueConfigurationElement keyValueConfigurationElement   Configuration AppSettings Settings key               if  keyValueConfigurationElement    null                                string value   keyValueConfigurationElement Value                  if   string IsNullOrEmpty value   result   value                                  return result              endregion Methods     Just for something to do  I refactored the top answer into a class  The usage is something like    ConfigMan configMan   new ConfigMan this GetType   Assembly Location   var setting   configMan GetAppSetting  AppSettingsKey

User · Answer

Why not to use     ProjectNamespace  Properties Settings Default  KeyProperty  for C  My Settings  KeyProperty  for VB NET   You just have to update visually those properties at design-time through    Solution Project - gt Properties- gt Settings

User · Answer

Use add existing item  select the app config from dll project   Before clicking add  use the little down arrow on the right hand side of the add button to  add as link   I do this all the time in my dev

[c#] Equivalent to 'app.config' for a library (DLL)

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