ASP.NET Core Docker environment variables if apply migration

Question

I have an ASP.NET Core application running in Docker and I need to pass to the container (at start) a bool variable whether on not to apply the migration.

For example:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
  if(newDB)
    Seed(true);
  else
    Seed(false);

 ...
}

Miq · Accepted Answer · 2018-06-08 13:58:45Z

1

You can use a configuration variable which value will be overridden an by environment variable on run.

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

        Configuration = builder.Build();
    }

public IConfigurationRoot Configuration { get; }

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
   var newDB = Convert.ToBoolean(Configuration["NewDB"]));
(...)

appsettings.json:

{
  "Logging": {
    (..)
   },
  "NewDB": false
}

And when running container pass: docker run -e APP_NewDB='true' ...

edited Jun 8, 2018 at 13:58

answered Jun 8, 2018 at 12:25

Miq

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4 Comments

Bug Over a year ago

I get an exception saying Unhandled Exception: System.FormatException: Could not parse the JSON file. Error on line number '27': '},....

Miq Over a year ago

are you not missing any comma in your json file? Please share it if you can.

Bug Over a year ago

{ "Logging": { "IncludeScopes": false, "LogLevel": { "Default": "Warning" } }, { "NewDB": false } }

Miq Over a year ago

You sholdn't use another braces around the newDB param - braces indicate another struct and you didn't name it, hence the error. Correct one: { "Logging": { "IncludeScopes": false, "LogLevel": { "Default": "Warning" } }, "NewDB": false }

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