.NET Core get connection string from appsettings.json

Question

I develop a simple web app and, in the future, I want to do it as multi-tenancy.

So I want to write the connection string straight into OnConfiguring method:

public class ApplicationContext : DbContext {     public DbSet<User> Users { get; set; }      protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)     {         optionsBuilder.UseSqlServer("connection string from appsettings.json");         base.OnConfiguring(optionsBuilder);     } } 

Startup class:

public void ConfigureServices(IServiceCollection services) {     services.AddDbContext<ApplicationContext>();     services.AddMvc(); } 

How can I extract connection string from appsettings.json into ApplicationContext class?

I wouldn't like to create any constructors for ApplicationContext class.

Answer 1

Let's imagine that you have .NET Core application and your appsettings.json file looks like this:

{   "Logging": {     "IncludeScopes": false,     "LogLevel": {       "Default": "Debug",       "System": "Information",       "Microsoft": "Information"     }   },   "Production": {     "SqliteConnectionString": "Filename=./MyDatabase.sqlite"   } } 

You can get SqliteConnectionString value from Startup.cs like this:

public void ConfigureServices(IServiceCollection services) {     var connection = Configuration["Production:SqliteConnectionString"];      services.AddDbContext<MyContext>(options =>         options.UseSqlite(connection)     );     ....  } 

And then in your DBContext you should add constructor that accepts DbContextOptions:

public class MyContext : DbContext {     public MyContext (DbContextOptions<MyContext> options) : base(options)     { }      ... } 

Answer 2

.NET Core 2.0

Add this class:

// Requires NuGet package Microsoft.Extensions.Configuration.Json  using Microsoft.Extensions.Configuration; using System.IO;  namespace RutarBackgroundServices.AppsettingsJson {     public static class AppSettingsJson     {         public static string ApplicationExeDirectory()         {             var location = System.Reflection.Assembly.GetExecutingAssembly().Location;             var appRoot = Path.GetDirectoryName(location);              return appRoot;         }          public static IConfigurationRoot GetAppSettings()         {             string applicationExeDirectory = ApplicationExeDirectory();              var builder = new ConfigurationBuilder()             .SetBasePath(applicationExeDirectory)             .AddJsonFile("appsettings.json");              return builder.Build();         }       } } 

Get the value for the key "MssqlConnectionString" from the "appsettings.json" file:

var appSettingsJson = AppSettingsJson.GetAppSettings(); var connectionString = appSettingsJson["MssqlConnectionString"]; 

Create the file "appsettings.json" in the root directory of your project:

{   "MssqlConnectionString": "Server=yourip; Database=yourdbname; User Id=yourusername; Password=yourpassword; Pooling=true;",   "Db2ConnectionString": "Database=yourdbname;UserID=yourusername;Password=yourpassword;Server=yourip:yourport",   "SomeOtherKey": "SomeOtherValue" }