如何将appsettings.json文本作为Model类中的SQL连接字符串传递？ （具体例子）

Question

I am migrating a ASP.NET project into ASP.NET Core and I was trying to implement DbContext functionality in .NET Core. I am trying to pass different SQL Server information to the optionsBuilder that I am passing as a parameter to the base constructor. I have the following context model class:

public partial class CompanyFormsContext : DbContext
{
        public CompanyFormsContext() : base (CreateOptions(null))
        {}

        public CompanyFormsContext(string connName) : base (CreateOptions(connName))
        {}

        //NEED TO CONNECT CONFIGURATION HERE
        private static DbContextOptions<CompanyFormsContext> CreateOptions(string connName)
        {
            var optionsBuilder = new DbContextOptionsBuilder<CompanyFormsContext>();

            if (connName == null)
            {
                optionsBuilder.UseSqlServer("Server=(localdb)\\projectsv13;Database=coforms;Trusted_Connection=True;");
            }
            else
            {
                //THIS IS HOW IM TRYING TO MAKE IT
                //similar to --> Configuration["Data:CompanyFormsContext:ConnectionString"]"
                optionsBuilder.UseSqlServer(Configuration["Data:" + connName + ":ConnectionString"]);
            }

            return optionsBuilder.Options;
        }
...

I want to pass in my SQL Server information through the information in appsettings.json which is the following:

  "Data": {
    "CompanyFormsContext": {
      "ConnectionString": "Server=(localdb)\\projectsv13;Database=coforms;Trusted_Connection=True;"
    },
    "CompanyFormsContextQA": {
      "ConnectionString": "Server=(localdb)\\projectsv13;Database=coforms;Trusted_Connection=True;"
    }
  },

I have found the following question but I believe the syntax has changed a bit since the RC2 update because I cannot use the solutions or I'm doing it wrong.

Setting the SQL connection string for ASP.NET 5 web app in Azure

How could I use a syntax similar to Configuration["Data:CompanyFormsContext:ConnectionString"] for the SQL Server input? Or is there a better way of doing this? What should be in the Startup file specifically? I have the following:

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();
    Configuration = builder.Build();
}

public IConfigurationRoot Configuration { get; set; }

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();
    services.AddOptions();
}
...

If requested, I can simplify the question to specifically ask about using appsettings.json in the model class. I realize that I have extra information here for clarifying the specific situation.

Answer 1

Solution 1

Are you trying to load a different environment for QA? If so, you should use an environment variable in your project properties called:

ASPNETCORE_ENVIRONMENT : Development

or

ASPNETCORE_ENVIRONMENT : QA

Then modify launchSettings.json:

{
  ...
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "IIS Express (QA)": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "QA"
      }
    }
  }
}

You can then create a separate Startup.cs file for each environment called StartupDevelopment.cs and StartupQA.cs . This will allow different start-up profiles based on the environment.

Solution 2

Are you trying to load separate connection strings based on the context (different contexts in your application load different connections)? If so:

The best way to do this is not to use the Context to initialise the connection. This should be done in the ConfigureServices method in Startup.cs . You can set up your connection strings based on the key in your json files:

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Load the first connection string
    var connectionStringA = Configuration["Data:DefaultConnection:ConnectionStringA"];
    // Load the second connection string
    var connectionStringB = Configuration["Data:DefaultConnection:ConnectionStringB"];
    // Set up Entity Framework
    services.AddEntityFramework()
        .AddSqlServer()
        .AddDbContext<ContextA>(options => options.UseSqlServer(connectionStringA))
        .AddDbContext<ContextB>(options => options.UseSqlServer(connectionStringB));
}

Now your contexts will load the connection strings from the JSON files correctly.