Auto-modifying connection strings based on the environment

To help ease managing databases and connection strings for our team using shared infrastructure (and non-localhost development databases), we needed a way to easily configure database connection strings to:

  • Easily identify databases on a server - what project/environment is using it?
  • Make sure we don’t touch databases of other team members during development.
    • e.g. when creating or merging/rebasing migrations

We use Entity Framework Core and it turned out the easisest way to configure this was to:

  1. Only have a single “base” connection string in appsettings.json
  2. Append the current environment name to the Database.
    • e.g. MyDb_Production, MyDb_Staging etc.
  3. Append the machine name when in development to avoid conflicts with team members.
    • e.g. MyDb_Development_DEVW10MARTIN

This can be done in ConfigureServices when configuring EF Core:

public class Startup
    public Startup(IConfiguration configuration, IHostingEnvironment hostingEnvironment)
        Configuration = configuration;
        HostingEnvironment = hostingEnvironment;

    public IConfiguration Configuration { get; }

    public IHostingEnvironment HostingEnvironment { get; }

    public void ConfigureServices(IServiceCollection services)
        services.AddDbContextPool<MyDbContext>(options =>
            var connectionString = Configuration.GetConnectionString("MyDbConnection");

            var connectionStringBuilder = new SqlConnectionStringBuilder(connectionString);

            connectionStringBuilder.InitialCatalog += "_" + HostingEnvironment.EnvironmentName;

            if (HostingEnvironment.IsDevelopment())
                connectionStringBuilder.InitialCatalog += "_" + Environment.MachineName;
            connectionString = connectionStringBuilder.ConnectionString;


So for example for the appsettings.json file

  "ConnectionStrings": {
    "MyDbConnection": "Data;Initial Catalog=MyDatabase;User Id=someuser;Password=somepassword;"

You can safely develop using a single server for the whole team during development and quickly identify which system is using a database if you happen to run on a shared infrastructure, since the actual database names being used will be:

  • MyDatabase_Production
  • MyDatabase_Staging
  • MyDatabase_DevStaging
  • MyDatabase_Development_MACHINEDEV1
  • MyDatabase_Development_MACHINEDEV2
Martin A. Ullrich

Martin A. Ullrich

Martin A. Ullrich
Software Developer in the .NET space. Also do Java, Swift/ObjC and front-end stuff.

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