app config for a class library

Question

I cannot see a app config file generated for a class library by the VS2008 wizard  In my research I found that in an application only one app config exists    Is it a bad thing to add an app config manually to a class library or are there any other methods which will serve the purpose of an app config in class library   I need to store log4net config information inside the app config file

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I would recommend using Properties Settings to store values like ConnectionStrings and so on inside of the class library  This is where all the connection strings are stores in by suggestion from visual studio when you try to add a table adapter for example  enter image description here   And then they will be accessible by using this code every where in the clas library   var cs   Properties Settings Default   lt name of defined setting gt

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You generally should not add an app config file to a class library project  it won t be used without some painful bending and twisting on your part  It doesn t hurt the library project at all - it just won t do anything at all   Instead  you configure the application which is using your library  so the configuration information required would go there  Each application that might use your library likely will have different requirements  so this actually makes logical sense  too

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Your answer for a non manual creation of an app config is Visual Studio Project Properties Settings tab   When you add a setting and save  your app config will be created automatically  At this point a bunch of code is generated in a  yourclasslibrary Properties  namespace containing properties corresponding to your settings  The settings themselves will be placed in the app config s applicationSettings settings     lt configSections gt       lt sectionGroup name  applicationSettings  type  System Configuration ApplicationSettingsGroup  System  Version 4 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089   gt           lt section name  ClassLibrary Properties Settings  type  System Configuration ClientSettingsSection  System  Version 4 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089  requirePermission  false    gt       lt  sectionGroup gt   lt  configSections gt   lt applicationSettings gt       lt ClassLibrary Properties Settings gt           lt setting name  Setting1  serializeAs  String  gt               lt value gt 3 lt  value gt           lt  setting gt       lt  BookOneGenerator Properties Settings gt   lt  applicationSettings gt    If you added an Application scoped setting called Setting1   3 then a property called Setting1 will be created   These properties are becoming at compilation part of the binary and they are decorated with a DefaultSettingValueAttribute which is set to the value you specified at development time         ApplicationScopedSetting       DebuggerNonUserCode       DefaultSettingValue  3        public string Setting1               get                       return  string this  Setting1                      Thus as in your class library code you make use of these properties if a corresponding setting doesn t exist in the runtime config file  it will fallback to use the default value  That way the application won t crash for lacking a setting entry  which is very confusing first time when you don t know how these things work  Now  you re asking yourself how can specify our own new value in a deployed library and avoid the default setting value be used    That will happen when we properly configure the executable s app config  Two steps  1  we make it aware that we will have a settings section for that class library and 2  with small modifications we paste the class library s config file in the executable config   there s a method where you can keep the class library config file external and you just reference it from the executable s config   So  you can have an app config for a class library but it s useless if you don t integrate it properly with the parent application  See here what I wrote sometime ago  link

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I don t know why this answer hasn t already been given   Different callers of the same library will  in general  use different configurations  This implies that the configuration must reside in the executable application  and not in the class library   You may create an app config within the class library project  It will contain default configurations for items you create within the library  For instance  it will contain connection strings if you create an Entity Framework model within the class library   However  these settings will not be used by the executable application calling the library  Instead  these settings may be copied from the library dll config file into the app config or web config of the caller  so that they may be changed to be specific to the caller  and to the environment into which the caller is deployed   This is how it has been with  NET since Day 1

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Actually  for some rare case you could store app config in class libraries  by adding manually  and parse it by OpenExeConfiguration   var fileMap       new ExeConfigurationFileMap  ExeConfigFilename          quot C    somePath   someName config quot     System Configuration Configuration config       ConfigurationManager OpenMappedExeConfiguration fileMap       ConfigurationUserLevel None    You should really estimate the real need of this  For abstract data its not the best solution  but  quot Config Sections quot  could be very usefull   For example  we organised our N-Tier WCF architecture decoupled  without any metadata  simply by using Unity Container and Injection Factory based on Channel Factory T  We added externall ClassLibrary dll with just  Service Contract  Interfaces and common app config in order to read endpoints from clientsection  and easily add change them at one place

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You do want to add App config to your tests class library  if you re using a tracer logger  Otherwise nothing gets logged when you run the test through a test runner such as TestDriven Net   For example  I use TraceSource in my programs  but running tests doesn t log anything unless I add an App config file with the trace log configuration to the test class library too   Otherwise  adding App config to a class library doesn t do anything

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There is no automatic addition of app config file when you add a class library project to your solution   To my knowledge  there is no counter indication about doing so manualy  I think this is a common usage   About log4Net config  you don t have to put the config into app config  you can have a dedicated conf file in your project as well as an app config file at the same time   this link http   logging apache org log4net release manual configuration html will give you examples about both ways  section in app config and standalone log4net conf file

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In fact  the class library you are implementing  is retrieving information from app config inside the application that is consuming it  so  the most correct way to implement configuration for class libraries at  net in VS is to prepare app config in the application to configure everything it consumes  like libraries configuration   I have worked a little with log4net  and I found that the one who prepared the application always had a section for log4net configuration inside main app config   I hope you find this information useful   See you  and post comments about the solution you found   EDIT   At the next link you have an app config with the section for log4net   http   weblogs asp net tgraham archive 2007 03 15 a-realistic-log4net-config aspx

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Jon  a lot of opinion has been given that didn t correctly answer your question   I will give MY OPINION and then tell you how to do exactly what you asked for   I see no reason why an assembly couldn t have its own config file  Why is the first level of atomicy  is that a real word   be at the application level  Why not at the solution level  It s an arbitrary  best-guess decision and as such  an OPINION  If you were to write a logging library and wanted to include a configuration file for it  that would be used globally  why couldn t you hook into the built-in settings functionality  We ve all done it     tried to provide  powerful  functionality to other developers  How  By making assumptions that inherently translated to restrictions  That s exactly what MS did with the settings framework  so you do have to  fool it  a little   To directly answer your question  simply add the configuration file manually  xml  and name it to match your library and to include the  config  extension  Example   MyDomain Mylibrary dll Config  Next  use the ConfigurationManager to load the file and access settings   string assemblyPath   new Uri Assembly GetExecutingAssembly   CodeBase  AbsolutePath  Configuration cfg   ConfigurationManager OpenExeConfiguration assemblyPath   string result   cfg AppSettings Settings  TEST SETTING   Value    Note that this fully supports the machine config heierarchy  even though you ve explicitly chosen the app config file  In other words  if the setting isn t there  it will resolve higher  Settings will also override machine config entries

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If you want to configure your project logging using log4Net  while using a class library  There is no actual need of any config file  You can configure your log4net logger in a class and can use that class as library   As log4net provides all the options to configure it   Please find the code below   public static void SetLogger string pathName  string pattern                        Hierarchy hierarchy    Hierarchy LogManager GetRepository                 PatternLayout patternLayout   new PatternLayout                patternLayout ConversionPattern   pattern              patternLayout ActivateOptions                 RollingFileAppender roller   new RollingFileAppender                roller AppendToFile   false              roller File   pathName              roller Layout   patternLayout              roller MaxSizeRollBackups   5              roller MaximumFileSize    1GB               roller RollingStyle   RollingFileAppender RollingMode Size              roller StaticLogFileName   true              roller ActivateOptions                hierarchy Root AddAppender roller                MemoryAppender memory   new MemoryAppender                memory ActivateOptions                hierarchy Root AddAppender memory                hierarchy Root Level   log4net Core Level Info              hierarchy Configured   true            Now instead of calling XmlConfigurator Configure new FileInfo  app config    you can directly call SetLogger with desired path and pattern to set the logger in Global asax application start function     And use the below code to log the error           public static void getLog string className  string message                        log4net ILog iLOG   LogManager GetLogger className               iLOG Error message         Info  Fatal  Warn  Debug             By using following code you need not to write a single line neither in application web config nor inside the app config of library

[c#] app.config for a class library

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