passing docker environment variables to .net core

问题

I've followed this article and the code on the github doesn't compile, tutorial is outdated I think. (Configuration = builder.Build();) throws error. So how can I access env passed from docker?

docker-compose

  myproj:
    image: mcr.microsoft.com/dotnet/core/sdk:2.2
    restart: on-failure
    working_dir: /MyProj
    command: bash -c "dotnet build MyProj.csproj && dotnet bin/Debug/netcoreapp2.2/MyProj.dll"
    ports:
      - 5001:5001
      - 5000:5000
    volumes:
      - "./MyProj:/MyProj"
    environment:
      DATABASE_HOST: database
      DATABASE_PASSWORD: Password

Startup.cs

public Service()
{
    Environment.GetEnvironmentVariable("DATABASE_PASSWORD"); // null
}

// This method gets called by the runtime. Use this method to add services to the container.
// For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
public void ConfigureServices(IServiceCollection services)
{
}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.Run(async (context) =>
    {
        context.Response.WriteAsync("Hello World!");
    });
}

回答1:

You can pass env variable in build argument. E.g.

--build-arg ASPNETCORE_ENVIRONMENT=Development

Use below variable to set value:

ASPNETCORE_ENVIRONMENT

Code:

var environmentName = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");

You can use above variable in your code for environment name .

回答2:

The standard approach to access environment variables in a .NET Core application is to use the static method

public static string GetEnvironmentVariable (string variable);

So in your case irrespective of what you pass either in the docker run command or through the launch settings file just use this method . As an example for getting the Database password use this

string dbPassword = Environment.GetEnvironmentVariable("DATABASE_PASSWORD");

Additionally be sure to define the environment variables part of the dockerfile by adding the line

ENV DATABASE_PASSWORD some_default_value_or_can_be_empty

来源：https://stackoverflow.com/questions/58318960/passing-docker-environment-variables-to-net-core

标签

Docker

asp.net-core