Two connection strings for local and hosting server

Question

I would like to ask if there is a way to tell ASP.NET Core 2 to choose different connection strings.

It is quite annoying to keep changing the connection string in the appsettings.json file every time I publish my website to the hosting server..

I am using this code to get connection string.

 services.AddDbContext<AppIdentityDbContext>(options => 
     options.UseSqlServer(Configuration["Data:WebDataBase:ConnectionString"]));

Maybe there is an easy way but I am thinking of using an if statement in my Startup.cs:

if (local) {
    services.AddDbContext<AppIdentityDbContext>(options => 
        options.UseSqlServer(Configuration["Data:WebDataBase1:ConnectionString"]));
}
else {
    services.AddDbContext<AppIdentityDbContext>(options => 
        options.UseSqlServer(Configuration["Data:WebDataBase2:ConnectionString"]));
}

But how can I set this local variable whether the server is my local computer or a live hosting server?

"Data": {
  "WebDataBase1": {
    "ConnectionString": "Data Source=DatasoruceName;Initial Catalog=DBname;Trusted_Connection=True;Integrated Security=True;"
  },

  "WebDataBase2": {
    "ConnectionString": "Data Source=DatasoruceName;Initial Catalog=DatabaseName;Trusted_Connection=True;Integrated Security=True;"
  }
}

Answer 1

Environment specific configuration is not supposed to be specified within code. ASP.NET Core has a mechanism for that which allows you to swap out the configuration dependending on what environment you run on.

While developing your application, you usually run in the Development environment. When you are deploying your application for production, the Production environment is used by default. But if you have other environments, you can totally make up new names for those too and have specific configurations for them. That all is explained in the Environments chapter of the documentation

What environments allow you to do is create multiple appsettings.json files. The ASP.NET Core by default comes with two files: appsettings.json and appsettings.Development.json.

The former is supposed to contain environment unspecific configuration; things that apply to all environments. The latter file contains development-specific configuration and for example adjusts the logging level so that you get more information during development. You can also use these files to specify a default connection string within appsettings.json and overwrite that for development within appsettings.Development.json.

Furthermore, the configuration file follows a very simple pattern: appsettings.<Environment>.json. So if you run in the Production environment, a file named appsettings.Production.json will be loaded if it exists. This mechanism allows you to configure all your environments differently without having to resort to detections within your code.

In addition, there is also the concept of user secrets during development. These are for development-specific configurations that do only apply to yourself but not for example to other members of your team. This is basically a per-machine configuration that allows you to overwrite both the appsettings.json and the appsettings.Development.json. This is described in the user secrets chapter.

Best practice is to avoid connection strings altogether within configuration files though, since you want to avoid that people that happen to have access to your configuration files (for example through your source code) can know the passwords to your database. In that case you can use other mechanisms, for example environment variables that are local to the process.

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In your case, where you are just using integrated security, and as such rely on the credentials of the current user, this is not that much of a problem. The only thing you are leaking is the database name. – So you can definitely start out with putting the connection strings into the appsettings files.

So for example, this is how you would configure your database context within your Startup’s ConfigureServices:

services.AddDbContext<AppIdentityDbContext>(options => 
    options.UseSqlServer(Configuration.GetConnectionString("WebDataBase"));

Your appsettings.Development.json would look like this:

{
  "ConnectionStrings": {
    "WebDataBase": "Data Source=DatasourceName;Initial Catalog=DBname;Trusted_Connection=True;Integrated Security=True;"
  }
}

And your appsettings.Production.json would look like this:

{
  "ConnectionStrings": {
    "WebDataBase": "Data Source=DatasourceName;Initial Catalog=DatabaseName;Trusted_Connection=True;Integrated Security=True;"
  }
}