How to read connection string in NET Core

Question

I want to read just a connection string from a configuration file and for this add a file with the name  appsettings json  to my project and add this content on it      ConnectionStrings        DefaultConnection    Server  localdb   mssqllocaldb Database aspnet-   WebApplica71d622 Trusted Connection True MultipleActiveResultSets true            Logging          IncludeScopes   false       LogLevel          Default    Debug        System    Information        Microsoft    Information              On ASP NET I used this    var temp ConfigurationManager ConnectionStrings  DefaultConnection   ConnectionString    Now how can I read  DefaultConnection  in C  and store it on a string variable in  NET Core

User · Accepted Answer

You can do this with the GetConnectionString extension-method:

string conString = Microsoft
   .Extensions
   .Configuration
   .ConfigurationExtensions
   .GetConnectionString(this.Configuration, "DefaultConnection");

System.Console.WriteLine(conString);

or with a structured-class for DI:

public class SmtpConfig
{
    public string Server { get; set; }
    public string User { get; set; }
    public string Pass { get; set; }
    public int Port { get; set; }
}

Startup:

public IConfigurationRoot Configuration { get; }


// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // http://developer.telerik.com/featured/new-configuration-model-asp-net-core/
    // services.Configure<SmtpConfig>(Configuration.GetSection("Smtp"));
    Microsoft.Extensions.DependencyInjection.OptionsConfigurationServiceCollectionExtensions.Configure<SmtpConfig>(services, Configuration.GetSection("Smtp"));

And then in the home-controller:

public class HomeController : Controller
{

    public SmtpConfig SmtpConfig { get; }
    public HomeController(Microsoft.Extensions.Options.IOptions<SmtpConfig> smtpConfig)
    {
        SmtpConfig = smtpConfig.Value;
    } //Action Controller


    public IActionResult Index()
    {
        System.Console.WriteLine(SmtpConfig);
        return View();
    }

with this in appsettings.json:

"ConnectionStrings": {
"DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-WebApplica71d622;Trusted_Connection=True;MultipleActiveResultSets=true"
},

"Smtp": {
    "Server": "0.0.0.1",
    "User": "[email protected]",
    "Pass": "123456789",
    "Port": "25"
  }

User · Answer

i have a data access library which works with both  net core and  net framework   the trick was in  net core  projects to keep the connection strings in a xml file named  app config   also for web projects   and mark it as  copy to output directory     lt  xml version  1 0  encoding  utf-8   gt   lt configuration gt     lt connectionStrings gt       lt add name  conn1  connectionString        providerName  System Data SqlClient    gt     lt  connectionStrings gt   lt  configuration gt    ConfigurationManager ConnectionStrings - will read the connection string       var conn1   ConfigurationManager ConnectionStrings  conn1   ConnectionString

User · Answer

The posted answer is fine but didn t directly answer the same question I had about reading in a connection string  Through much searching I found a slightly simpler way of doing this   In Startup cs  public void ConfigureServices IServiceCollection services                   Add the whole configuration object here      services AddSingleton lt IConfiguration gt  Configuration       In your controller add a field for the configuration and a parameter for it on a constructor  private readonly IConfiguration configuration   public HomeController IConfiguration config         configuration   config      Now later in your view code you can access it like   connectionString   configuration GetConnectionString  DefaultConnection

User · Answer

The way that I found to resolve this was to use AddJsonFile in a builder at Startup  which allows it to find the configuration stored in the appsettings json file  and then use that to set a private  config variable  public Startup IHostingEnvironment env                var builder   new ConfigurationBuilder                SetBasePath env ContentRootPath               AddJsonFile  appsettings json   optional  true  reloadOnChange  true               AddJsonFile   appsettings  env EnvironmentName  json   optional  true               AddEnvironmentVariables             config   builder Build            And then I could set the configuration string as follows   var connectionString    config GetConnectionString  DbContextSettings ConnectionString       This is on dotnet core 1 1

User · Answer

In 3 1 there is a section already defined for  quot ConnectionStrings quot  System Configuration ConnnectionStringSettings Define     quot ConnectionStrings quot          quot ConnectionString quot    quot     quot       Register  public void ConfigureServices IServiceCollection services         services Configure lt ConnectionStringSettings gt  Configuration GetSection  quot ConnectionStrings quot        Inject  public class ObjectModelContext   DbContext  IObjectModelContext         private readonly ConnectionStringSettings ConnectionStringSettings                 public ObjectModelContext DbContextOptions lt ObjectModelContext gt  options  IOptions lt ConnectionStringSettings gt  setting    base options                  ConnectionStringSettings   setting Value                    Use     public static void ConfigureContext DbContextOptionsBuilder optionsBuilder  ConnectionStringSettings connectionStringSettings                if  optionsBuilder IsConfigured    false                        optionsBuilder UseLazyLoadingProxies                              UseSqlServer connectionStringSettings ConnectionString

User · Answer

Too late  but after reading all helpful answers and comments  I ended up using Microsoft Extensions Configuration Binder extension package and play a little around to get rid of hardcoded configuration keys  My solution  IConfigSection cs public interface IConfigSection      ConfigurationExtensions cs public static class ConfigurationExtensions       public static TConfigSection GetConfigSection lt TConfigSection gt  this IConfiguration configuration  where TConfigSection   IConfigSection  new                 var instance   new TConfigSection            var typeName   typeof TConfigSection  Name          configuration GetSection typeName  Bind instance            return instance           appsettings json       quot AppConfigSection quot            quot IsLocal quot   true           quot ConnectionStringsConfigSection quot            quot ServerConnectionString quot   quot Server   Database MyDb Trusted Connection True  quot          quot LocalConnectionString quot   quot Data Source MyDb db quot            To access a strongly typed config  you just need to create a class for that  which implements IConfigSection interface Note  class names and field names should exactly match section in appsettings json  AppConfigSection cs public class AppConfigSection  IConfigSection       public bool IsLocal   get  set       ConnectionStringsConfigSection cs public class ConnectionStringsConfigSection   IConfigSection       public string ServerConnectionString   get  set        public string LocalConnectionString   get  set         public ConnectionStringsConfigSection                    set default values to avoid null reference if            section is not present in appsettings json         ServerConnectionString   string Empty          LocalConnectionString   string Empty           And finally  a usage example  Startup cs public class Startup       public Startup IConfiguration configuration                Configuration   configuration             public IConfiguration Configuration   get         public void ConfigureServices IServiceCollection services                   some stuff          var app   Configuration GetConfigSection lt AppConfigSection gt             var connectionStrings   Configuration GetConfigSection lt ConnectionStringsConfigSection gt              services AddDbContext lt AppDbContext gt  options   gt                        if  app IsLocal                                options UseSqlite connectionStrings LocalConnectionString                             else                               options UseSqlServer connectionStrings ServerConnectionString                                         other stuff          To make it neat  you can move above code into an extension method  That s it  no hardcoded configuration keys

User · Answer

You can use configuration extension method   getConnectionString   DefaultConnection    https   docs asp net projects api en latest autoapi Microsoft Extensions Configuration ConfigurationExtensions index html Microsoft Extensions Configuration ConfigurationExtensions GetConnectionString

User · Answer

ASP NET Core  in my case 3 1  provides us with Constructor injections into Controllers  so you may simply add following constructor    Route  api  controller      ApiController  public class TestController   ControllerBase       private readonly IConfiguration m config       public TestController IConfiguration config                m config   config              HttpGet      public string Get                   you can get connection string as follows         string connectionString   m config GetConnectionString  Default             Here what appsettings json may look like          ConnectionStrings              Default    YOUR CONNECTION STRING

User · Answer

This is how I did it  I added the connection string at appsettings json  quot ConnectionStrings quot      quot conStr quot    quot Server MYSERVER Database MYDB Trusted Connection True MultipleActiveResultSets true quot     I created a class called SqlHelper public class SqlHelper         this field gets initialized at Startup cs     public static string conStr       public static SqlConnection GetConnection                 try                       SqlConnection connection   new SqlConnection conStr               return connection                    catch  Exception e                        Console WriteLine e               throw                     At the Startup cs I used ConfigurationExtensions GetConnectionString to get the connection and I assigned it to SqlHelper conStr public Startup IConfiguration configuration                Configuration   configuration          SqlHelper connectionString   ConfigurationExtensions GetConnectionString this Configuration   quot conStr quot           Now wherever you need the connection string you just call it like this  SqlHelper GetConnection

User · Answer

See link for more info  https   docs microsoft com en-us ef core miscellaneous connection-strings  JSON                  ConnectionStrings              BloggingDatabase    Server  localdb   mssqllocaldb Database EFGetStarted ConsoleApp NewDb Trusted Connection True                    C  Startup cs  public void ConfigureServices IServiceCollection services        services AddDbContext lt BloggingContext gt  options   gt          options UseSqlServer Configuration GetConnectionString  BloggingDatabase          EDIT  aspnetcore  starting 3 1  https   docs microsoft com en-us aspnet core fundamentals configuration  view aspnetcore-3 1

User · Answer

There is another approach  In my example you see some business logic in repository class that I use with dependency injection in ASP  NET MVC Core 3 1   And here I want to get connectiongString for that business logic because probably another repository will have access to another database at all   This pattern allows you in the same business logic repository  have access to different databases   C   public interface IStatsRepository               IEnumerable lt FederalDistrict gt  FederalDistricts       class StatsRepository   IStatsRepository      private readonly DbContextOptionsBuilder lt EFCoreTestContext gt                  optionsBuilder   new DbContextOptionsBuilder lt EFCoreTestContext gt        private readonly IConfigurationRoot configurationRoot      public StatsRepository               IConfigurationBuilder configurationBuilder   new ConfigurationBuilder   SetBasePath Environment CurrentDirectory              AddJsonFile  appsettings json   optional  true  reloadOnChange  true          configurationRoot   configurationBuilder Build             public IEnumerable lt FederalDistrict gt  FederalDistricts                var conn   configurationRoot GetConnectionString  EFCoreTestContext            optionsBuilder UseSqlServer conn            using  var ctx   new EFCoreTestContext optionsBuilder Options                          return ctx FederalDistricts Include x   gt  x FederalSubjects  ToList                        appsettings json       Logging          LogLevel            Default    Information          Microsoft    Warning          Microsoft Hosting Lifetime    Information                AllowedHosts           ConnectionStrings          EFCoreTestContext    Data Source DESKTOP-GNJKL2V  MSSQLSERVER2014 Database Test Trusted Connection True MultipleActiveResultSets true

[c#] How to read connection string in .NET Core?

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