Passing application's connection string down to a Repository Class Library in ASP.NET 5 using the IConfigurationRoot

Question

I have an ASP.NET 5 MVC Web Application and in Startup.cs I see that the public property

IConfigurationRoot Configuration 

is being set to

Answer 1

I have a constructor in my repository class that accepts the db connection string as a parameter. This works for me when I add my repository for injection. In ConfigureServies() of the startup.cs file add this:

services.AddScoped<IRepos>(c => new Repos(Configuration["DbConnections:ConnStr1"]));

IRepos.cs is the interface, Repos.cs is the class that implements it. And of course Configuration is just a reference to the built IConfigurationRoot object.

Answer 2

If ConfigureServices in your project's startUp.cs contains

services.AddEntityFramework()
             .AddSqlServer()
             .AddDbContext<YourDbContext>(options =>
                 options.UseSqlServer(Configuration["Data:DefaultConnection:ConnectionString"]));

and your repository cs file is having constructor injection as shown below

public class MyRepo : IRepo
{
    private readonly YourDbContext dbContext;
    public MyRepo(YourDbContext ctx)
    {
        dbContext = ctx;
    }
}

YourDbContext will be automatically resolved.

Answer 3

A slightly different approach would be to make a static class in your Class Library on which you call a method from the Configure(..)-method in Startup.cs:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    ...
    ConnectionManager.SetConfig(Configuration);
}

In this case, I've added Configuration as a Singleton in ConfigureServices:

services.AddSingleton(_ => Configuration);

My ConnectionManager looks like this:

public class ConnectionManager
{
    private static IConfiguration currentConfig;

    public static void SetConfig(IConfiguration configuration)
    {
        currentConfig = configuration;
    }

    /// <summary>
    /// Get a connection to the database.
    /// </summary>
    public static SqlConnection GetConnection
    {
        get
        {
            string connectionString = currentConfig.GetConnectionString("MyConnection");
            // Create a new connection for each query.
            SqlConnection connection = new SqlConnection(connectionString);
            return connection;
        }
    }
}

This may or may not have some issues regarding object lifetimes and such, and I'm certainly no fan of static classes but as far as I can tell it's a viable approach. Instead of passing Configuration you could even extract the ConnectionString from the config-file and send only that.

Answer 4

What you need is to create a class in class library project to access the appsettings.json in website project and return connection string.

{
    private static string _connectionString;

    public static string GetConnectionString()
    {
        if (string.IsNullOrEmpty(_connectionString))
        {
            var builder = new ConfigurationBuilder()
           .AddJsonFile("appsettings.json");
            Configuration = builder.Build();
            _connectionString = Configuration.Get<string>("Data:MyDb:ConnectionString");
        }
        return _connectionString;
    }
    public static IConfigurationRoot Configuration { get; set; }

}

Answer 5

on your Startup.cs file add the following method

public void ConfigureServices(IServiceCollection services) {
    services.AddSingleton(_ => Configuration);
}

then update your BaseRepo class like this

public class BaseRepo {
    private readonly IConfiguration config;

    public BaseRepo(IConfiguration config) {
        this.config = config;
    }

    public SqlConnection GetOpenConnection() {
        string cs = config["Data:DefaultConnection:ConnectionString"];
        SqlConnection connection = new SqlConnection(cs);
        connection.Open();
        return connection;
    }
}

Answer 6

ASP.NET provides its own way of passing around configuration settings.

Suppose you have the this in your appSettings.json:

{
  "Config": {
    "Setting1": 1,
    "Setting2": "SO"
  }
}

Then you need a class like this:

public class MyConfiguration
{
    public int Setting1 { get; set; }

    public string Setting2 { get; set; }
}

This allows you to configure your service with this configuration by adding the following line

services.Configure<MyConfigurationDto>(Configuration.GetSection("Config"));

to ConfigureServices.

You can then inject the configuration in constructors by doing the following:

public class SomeController : Controller
{
    private readonly IOptions<MyConfiguration> config;

    public ServiceLocatorController(IOptions<MyConfiguration> config)
    {
        this.config = config;
    }

    [HttpGet]
    public IActionResult Get()
    {
        return new HttpOkObjectResult(config.Value);
    }
}

This example is for controllers. But you can do the same with other layers of you application.