Using app config in Net Core

Question

I have problem  I need to write a program in  Net Core C   which use app config like this    lt  xml version  1 0  encoding  utf-8    gt   lt configuration gt     lt configSections gt       lt section name  custom  type  ConfigurationSample CustomConfigurationSection  ConfigurationSample   gt     lt  configSections gt     lt connectionStrings gt       lt add name  sampleDatabase  connectionString  Data Source localhost SQLExpress Initial Catalog SampleDatabase Integrated Security True   gt     lt  connectionStrings gt     lt appSettings gt       lt add key  sampleApplication  value  Configuration Sample   gt     lt  appSettings gt     lt custom gt       lt customConfigurations gt         lt add key  customSample  name  Mickey Mouse  age  83   gt       lt  customConfigurations gt     lt  custom gt   lt  configuration gt    and I write   string connectionString   ConfigurationManager ConnectionStrings  sampleDatabase   ConnectionString  Console WriteLine connectionString       read appSettings configuration string appSettingValue   ConfigurationManager AppSettings  sampleApplication    Console WriteLine appSettingValue     and it is example from the internet so I thought would work  but I am getting exceptions   System Configuration ConfigurationErrorsException   Error Initializing the configuration system   Inner Exception TypeLoadException  Could not load type  System Configuration InternalConfigurationHost  from assembly  CoreCompat System Configuration  Version 4 2 3 0  Culture neutral  PublicKeyToken null  because the method  get bundled machine config  has no implementation  no RVA     I downloaded via NuGet - Install-Package CoreCompat System Configuration -Version 4 2 3-r4 -Pre and still don t work  Maybe someone can help me

User · Answer

To get started with dotnet core  SqlServer and EF core the below DBContextOptionsBuilder would sufice and you do not need to create App config file  Do not forget to change the sever address and database name in the below code  protected override void OnConfiguring DbContextOptionsBuilder options            gt  options UseSqlServer   quot Server  localdb  MSSQLLocalDB Database TestDB Trusted Connection True  quot     To use the EF core SqlServer provider and compile the above code install the EF SqlServer package dotnet add package Microsoft EntityFrameworkCore SqlServer  After compilation before running the code do the following for the first time dotnet tool install --global dotnet-ef dotnet add package Microsoft EntityFrameworkCore Design dotnet ef migrations add InitialCreate dotnet ef database update  To run the code dotnet run

User · Answer

It is possible to use your usual System Configuration even in  NET Core 2 0 on Linux  Try this test example   Created a  NET Standard 2 0 Library  say MyLib dll  Added the NuGet package System Configuration ConfigurationManager v4 4 0  This is needed since this package isn t covered by the meta-package NetStandard Library v2 0 0  I hope that changes  All your C  classes derived from ConfigurationSection or ConfigurationElement go into MyLib dll  For example MyClass cs derives from ConfigurationSection and MyAccount cs derives from ConfigurationElement  Implementation details are out of scope here but Google is your friend  Create a  NET Core 2 0 app  e g  a console app  MyApp dll    NET Core apps end with  dll rather than  exe in Framework  Create an app config in MyApp with your custom configuration sections  This should obviously match your class designs in  3 above  For example     lt  xml version  quot 1 0 quot  encoding  quot utf-8 quot   gt   lt configuration gt     lt configSections gt       lt section name  quot myCustomConfig quot  type  quot MyNamespace MyClass  MyLib quot    gt     lt  configSections gt     lt myCustomConfig gt       lt myAccount id  quot 007 quot    gt     lt  myCustomConfig gt   lt  configuration gt   That s it - you ll find that the app config is parsed properly within MyApp and your existing code within MyLib works just fine  Don t forget to run dotnet restore if you switch platforms from Windows  dev  to Linux  test   Additional workaround for test projects If you re finding that your App config is not working in your test projects  you might need this snippet in your test project s  csproj  e g  just before the ending  lt  Project gt    It basically copies App config into your output folder as testhost dll config so dotnet test picks it up     lt  -- START  This is a buildtime work around for https   github com dotnet corefx issues 22101 -- gt     lt Target Name  quot CopyCustomContent quot  AfterTargets  quot AfterBuild quot  gt       lt Copy SourceFiles  quot App config quot  DestinationFiles  quot   OutDir  testhost dll config quot    gt     lt  Target gt     lt  -- END  This is a buildtime work around for https   github com dotnet corefx issues 22101 -- gt

User · Answer

You can use Microsoft Extensions Configuration API with any  NET Core app  not only with ASP NET Core app  Look into sample provided in the link  that shows how to read configs in the console app  In most cases  the JSON source  read as  json file  is the most suitable config source      Note  don t be confused when someone says that config file should be appsettings json  You can use any file name  that is suitable for you and file location may be different - there are no specific rules    But  as the real world is complicated  there are a lot of different configuration providers    File formats  INI  JSON  and XML  Command-line arguments Environment variables   and so on  You even could use write a custom provider  Actually  app config configuration file was an XML file  So you can read settings from it using XML configuration provider  source on github  nuget link   But keep in mind  it will be used only as a configuration source - any logic how your app behaves should be implemented by you  Configuration Provider will not change  settings  and set policies for your apps  but only read data from the file

User · Answer

I have a  Net Core 3 1 MSTest project with similar issue  This post provided clues to fix it   Breaking this down to a simple answer for  Net core 3 1    add ensure nuget package  System Configuration ConfigurationManager to project add your app config xml  to project    If it is a MSTest project    rename file in project to testhost dll config  OR Use post-build command provided by DeepSpace101

[c#] Using app.config in .Net Core

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