Confusion between .config files and Azure settings on ASP.Net core web app

Question

I have built a project (to provide an API to a SPA web app) as a Asp.Net Core Web Application (.net framework) with the WebApi option (VS 2017 Community). This created a project with an app.config file and no web.config file. I have a section in app.config that I read using System.Configuration.ConnectionManager.ConnectionStrings['MainDb'] in my Startup.cs class which works fine locally.

When I deploy the app to Azure and set a 'MainDb' connection string in the portal, it does not get read by the web app. I have set these via the portal directly and via the settings pane available via the Azure server explorer in VS2017. In the server explorer I can see a web.config file but no app.config file, the web.config file has no connectionstring node but the web app seems to be seeing the connection string that was in app.config when I deployed.

I am somewhat confused as to the interaction between the app.config and the web.config here - where do I need to declare my connection string so that it can be overridden by the Azure portal setting?

Yeah, it does. Looks like project was started as an 'Empty' one rather than a web app and stuff added to it. Should the connection strings go in appsettings then? — Rikalous
Yeah, it should. You can check this article I wrote for more guidance: joonasw.net/view/asp-net-core-1-configuration-deep-dive. You should add it to a ConnectionStrings section, and read it using the Core configuration APIs instead of the one you were using. — juunas
I added an appsettings.json file to the project and placed my connection strings in there; app.config no longer used. Following the advice in junnas's article to read them out again worked and they are picked up in Azure as expected. — Rikalous

juunas juunas · Accepted Answer · 2017-07-13T09:52:43

Typically in ASP.NET Core we use an appsettings.json file for configuration. Though there are many other options too (XML, user secrets etc.): https://joonasw.net/view/asp-net-core-1-configuration-deep-dive.

So you would have an appsettings.json file like this:

{
  "ConnectionStrings": {
    "MainDb": "Data Source=.;Initial Catalog=MainDb;Integrated Security=True"
  }
}

You can then read it by accessing the IConfiguration object in Startup:

public class Startup
{
    public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
        Configuration = builder.Build();
    }

    public IConfiguration Configuration { get; set; }

    public void ConfigureServices(IServiceCollection services)
    {
        string connStr = Configuration.GetConnectionString("MainDb);
    }
}

GetConnectionString("name") is actually a shorthand for Configuration.GetSection("ConnectionStrings")["name"].

Confusion between .config files and Azure settings on ASP.Net core web app

1 Answers