How to extract the connection string and pass it as program argument

[Kralizek]

I'm stitching together different snippets from multiple sources (discussions, twitter, reddit and so on) and I feel I'm getting closer and closer to get my application being fully built on Aspire despite many components not being super friendly to its model.

Now I'm at the stage that I want to run a console application we use to initialize and seed our database. This operation is idempotent, so I don't mind adding it to the AppHost. Unfortunately, it needs the connection string to the database to be passed as an argument and I can't find a way to get it.

using AppHost.Extensions;
using Projects;

var builder = DistributedApplication.CreateBuilder(args);

var adminUiClientId = builder.AddParameter("AdminUiClient");
var adminUiClientSecret = builder.AddParameter("AdminUiClientSecret");
var adminUiLicenseKey = builder.AddParameter("AdminUiLicenseKey");

var sqlPasswordResource = builder.AddParameter("SqlServerPassword");

var mssql = builder.AddSqlServer("db", sqlPasswordResource)
    .PublishAsConnectionString()
    .WithHealthCheck()
    .WithDataVolume();

var db = mssql.AddDatabase("Database", "identity-manager")
    .AddConnectionStringData(new Dictionary<string, object>
    {
        ["MultipleActiveResultSets"] = true,
        ["Encrypt"] = false
    }); // source: https://github.com/dotnet/aspire/discussions/3605

var legacyDb = mssql.AddDatabase("LegacyDatabase", "legacy")
    .AddConnectionStringData(new Dictionary<string, object>
    {
        ["MultipleActiveResultSets"] = true,
        ["Encrypt"] = false
    });

var legacy = builder.AddProject<LegacyAPI>("legacy", "https")
    .WaitFor(mssql) // source: https://github.com/davidfowl/WaitForDependenciesAspire
    .WithReference(db);

var auth = builder.AddProject<AuthService>("auth", "https")
    .WaitFor(mssql)
    .WithReference(db)
    .WithReference(legacyDb);

const string protocol = "https";

var dbOpsRunner = builder.AddProject("dbOpsRunner", "../DatabaseOpsRunner/DatabaseOpsRunner.csproj")
    .WaitFor(mssql)
    .WithArgs(["apply", "all", $"{db}"]) // insert connection string here
    .WithEnvironment("ADMINUI__ADMINUICLIENTID", adminUiClientId)
    .WithEnvironment("ADMINUI__UIURL", "https://localhost:7089") // add endpoint to auth
    .WithEnvironment("ADMINUI__AUTHORITYURL", auth.GetEndpoint(protocol))
    .WithEnvironment("ADMINUI__LICENSEKEY", adminUiLicenseKey);

EndpointReference adminEndpoint = default!;

var admin = builder.AddProject<Admin>("admin", "https")
    .WaitForCompletion(dbOpsRunner)
    .WaitFor(mssql)
    .WithEnvironment("AdminUi__AdminUiClientId", adminUiClientId)
    .WithEnvironment("AdminUi__AdminUiClientSecret", adminUiClientSecret)
    .WithEnvironment("AdminUi__LicenseKey", adminUiLicenseKey)
    .WithEnvironment("AdminUi__AuthorityUrl", auth.GetEndpoint(protocol))
    .WithEnvironment("AdminUi__UiUrl", () => adminEndpoint.Url)
    .WithReference(db);

adminEndpoint = admin.GetEndpoint(protocol);

// source: https://github.com/davidfowl/AspireYarp
// builder.AddYarp("login")
//     .Route("legacy", legacy, path: "/accounts", preservePath: true)
//     .Route("auth", auth, path: "/");
// .WithHttpEndpoint(port: 8001)
// .WithReference(auth)
// .LoadFromConfiguration("ReverseProxy");

builder.Build().Run();

I tried the following:

.WithArgs(["apply", "all", $"{db}"])

// Result: the whole object gets printed out.

.WithArgs(["apply", "all", $"{await db.Resource.GetConnectionStringAsync()}"])

// Result:

Unhandled exception. System.InvalidOperationException: The endpoint `tcp` is not allocated for the resource `db`.
   at Aspire.Hosting.ApplicationModel.EndpointReference.get_AllocatedEndpoint() in /_/src/Aspire.Hosting/ApplicationModel/EndpointReference.cs:line 107
   at Aspire.Hosting.ApplicationModel.EndpointReference.get_Port() in /_/src/Aspire.Hosting/ApplicationModel/EndpointReference.cs:line 79
   at Aspire.Hosting.ApplicationModel.EndpointReferenceExpression.GetValueAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting/ApplicationModel/EndpointReference.cs:line 179
   at Aspire.Hosting.ApplicationModel.ReferenceExpression.GetValueAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting/ApplicationModel/ReferenceExpression.cs:line 66
   at Aspire.Hosting.ApplicationModel.ReferenceExpression.GetValueAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting/ApplicationModel/ReferenceExpression.cs:line 66
   at Aspire.Hosting.ApplicationModel.ReferenceExpression.GetValueAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting/ApplicationModel/ReferenceExpression.cs:line 66
   at Program.<Main>$(String[] args) in C:\Development\App\tools\AppHost\Program.cs:line 42
   at Program.<Main>(String[] args)

Process finished with exit code -532,462,766.

Another issue I'm having is passing the endpoint to a service to the console app. The tricky part is that I want the service to wait for the console app to terminate before it starts. For now I have hardcoded the port number.

See

.WithEnvironment("ADMINUI__UIURL", "https://localhost:7089") // add endpoint to auth

[davidfowl]

It's not intuitive how you'd make this work:

.WithArgs(context =>
{
  context.Args.Add("apply");
  context.Args.Add("all");
  context.Args.Add(new ConnectionStringReference(db.Resource, optional: false)));
})

We need to add the string interpolation overload to adding args.

Another issue I'm having is passing the endpoint to a service to the console app. The tricky part is that I want the service to wait for the console app to terminate before it starts. For now I have hardcoded the port number.

I'm not fully understanding this. You want the console app to terminate before which service starts?

[kwaazaar]

I used a resource in an interpolated string. But even though it holds just a string, it's ToString does not return its value. So I had to use $"{customerCode.Resource.Value}__Bus__ConnectionString" instead of $"{customerCode}__Bus__ConnectionString". Took me hours to figure this out.

So basically it's pretty straightforward and you don't need ConnectionStringReference (anymore):

var builder = DistributedApplication.CreateBuilder(args);

var customerCode = builder.AddParameter("customerCode"); // this is a Resource, not a string!
var saPassword = builder.AddParameter("saPassword", secret: true);

var sqlServer = builder
    .AddSqlServer("sql", password: saPassword, port: 14329)
    .WithDataVolume(); // Keep data between restarts

var dbMaster = sqlServer.AddDatabase("master");
var dbCustomer = sqlServer.AddDatabase(customerCode.Resource.Value);

builder
    .AddProject<Projects.MessageProcessor>("MessageProcessor")
    .WithEnvironment($"{customerCode.Resource.Value}__CustomerSettings__DbConnectionString", dbCustomer);

builder.Build().Run();

[davidfowl]

This should be fixed in 9.2, why is the name of the environment variable the value here?

[kwaazaar]

.WithEnvironment takes name, then value. Are you confusing it with .WithReference, which takes value then (connection)name?
Otherwise I'm not sure what you mean.

[davidfowl]

WithEnvironment($"{customerCode.Resource.Value}__CustomerSettings__DbConnectionString", dbCustomer);

I see you wanted the value of the parameter to be part of the name of the environment variable.

PS: This won’t be publishable as the parameter has no value at the time this code is run.

[davidfowl]

I wrote this doc https://gist.github.com/davidfowl/b408af870d4b5b54a28bf18bffa127e1 (it's BIG), please let me know if it helps with your understanding and feel free to leave any feedback.