Category: Aspire

Aspire Blazor WebAssembly and WebAPI


Aspire is the new visualizer – see

I am very fond of WebAPI  –  it allows for all people to see the functionality of a site , in a programmatic way ( side note: , my nuget package, , allows to make workflows from your WebAPI)

And Blazor WebAssembly is a nice addition that the WebAPI . I am talking about Interactive WebAssembly (  )  . I do want ( for the moment ) to use Interactive Server because

  1. it is easy to forget to add functionality to the WebAPI
  2. it is not separating UI from BL

So I decided to add an Blazor WebAssembly and WebAPI into Aspire to see how they work together.

The first problem that  I have is how to transmit the WebAPI URL to the Blazor WebAssembly . Think that is not Interactive Server or Auto – in order to have the environment or configuration . Blazor Interactive WebAssembly  are just static files that are downloaded to the client. And they are executed in the browser.

But I have tried with adding to the Environment in usual way

.WithEnvironment(ctx =&gt;
if (api.Resource.TryGetAllocatedEndPoints(out var end))
if (end.Any())
	ctx.EnvironmentVariables["HOSTAPI"] = end.First().UriString;


And no use!

After reading ASP.NET Core Blazor configuration | Microsoft Learn  and aspire/src/Microsoft.Extensions.ServiceDiscovery at main · dotnet/aspire ( and API review for Service Discovery · Issue #789 · dotnet/aspire ( I realized that the ONLY way is to put in wwwroot/appsettings.json

So I came with the following code that tries to write DIRECTLY to wwwroot/appsettings.json file

namespace Aspire.Hosting;
public static class BlazorWebAssemblyProjectExtensions
    public static IResourceBuilder<ProjectResource> AddWebAssemblyProject<TProject>(
        this IDistributedApplicationBuilder builder, string name,
        IResourceBuilder<ProjectResource> api) 
        where TProject : IServiceMetadata, new()
        var projectbuilder = builder.AddProject<TProject>(name);
        var p=new TProject();
        string hostApi= p.ProjectPath;
        var dir = Path.GetDirectoryName(hostApi);
        var wwwroot = Path.Combine(dir, "wwwroot");
        if (!Directory.Exists(wwwroot)) {
        var file = Path.Combine(wwwroot, "appsettings.json");
        if (!File.Exists(file))
            File.WriteAllText(file, "{}");
        projectbuilder =projectbuilder.WithEnvironment(ctx =>
            if (api.Resource.TryGetAllocatedEndPoints(out var end))
                if (end.Any())
                    var fileContent = File.ReadAllText(file);

                    Dictionary<string, object>? dict;
                    if (!string.IsNullOrWhiteSpace(fileContent))
                        dict = new Dictionary<string, object>();
                        dict = JsonSerializer.Deserialize<Dictionary<string,object>>(fileContent!);

                    dict["HOSTAPI"] = end.First().UriString;                    
                    JsonSerializerOptions opt = new JsonSerializerOptions(JsonSerializerOptions.Default)
                            { WriteIndented=true};

        return projectbuilder;


And in Aspire

var api = builder.AddProject<Projects.ExampleWebAPI>(nameof(Projects.ExampleWebAPI));
builder.AddWebAssemblyProject<Projects.ExampleBlazorApp>(nameof(Projects.ExampleBlazorApp), api);

And in Blazor Interactive WebAssembly

var hostApi = builder.Configuration["HOSTAPI"];
if (string.IsNullOrEmpty(hostApi))
    hostApi = builder.HostEnvironment.BaseAddress;
    var dict = new Dictionary<string, string?> { { "HOSTAPI", hostApi } };

builder.Services.AddKeyedScoped("db",(sp,_) => new HttpClient { BaseAddress = new Uri(hostApi) });

What about deploying the code to production ? Well, I think that is better to wrote yourself to wwwroot/appsettings.json and remove the data . But I will try to deploy and let you know….

Aspire , containers and dotnet watch

Aspire is the new visualizer – see

If you use dotnet run ( or Visual Studio)  with an Aspire host that instantiate some containers  , then , when you stop the project, the container is released.

But, if you use

dotnet watch run –nohotreload

then the containers are not  deleted. The nice solution is to investigate dotnet watch and Aspire . And maybe fill a bug.

The easy ? Delete the containers first !

void DeleteDockerContainers()
    var process = new Process
        StartInfo = new ProcessStartInfo
            FileName = "powershell.exe",
            Arguments = $$"""
-Command "docker rm -f $(docker ps -a -q)"
            RedirectStandardOutput = true,
            UseShellExecute = false,
            CreateNoWindow = true,
    while (!process.StandardOutput.EndOfStream)
        var line = process.StandardOutput.ReadLine();

Aspire, Sql Server Docker Container and multiple Connections strings

Aspire is the new visualizer – see

When creating a Docker container with Sql Server , the connection that is returned is without database – means that , usually, is connecting to the master.

That’s not that we usually want, so the following code is means that WebAPI will be connected to master

var builder = DistributedApplication.CreateBuilder(args);
var rb= builder.AddSqlServerContainer("Db2Gui", "<YourStrong@Passw0rd>");

Instead , do what they do – but add the database

var builder = DistributedApplication.CreateBuilder(args);

var rb= builder.AddSqlServerContainer("Db2Gui", "<YourStrong@Passw0rd>");

        var connectionStringName = $"ConnectionStrings__";
        var res=rb.Resource;
        var cn = res.GetConnectionString();
        ctx.EnvironmentVariables[connectionStringName+ "ApplicationDBContext"] = cn+ $";database=tests;";
        ctx.EnvironmentVariables[connectionStringName+ "NorthwindDBContext"] = cn + $";database=northwind;";
        ctx.EnvironmentVariables[connectionStringName+ "PubsDBContext"] = cn + $";database=pubs;";
    //.WithReference(rb, "")

It is true that you can make the following :

    .WithReference(rb.AddDatabase("tests"), "ApplicationDBContext")
    .WithReference(rb.AddDatabase("northwind"), "NorthwindDBContext")
    .WithReference(rb.AddDatabase("pubs"), "PubsDBContext")
    .WithReference(rb.AddDatabase("NotCreated"), "NotCreated")


But it does not CREATE the database ( and it is a good thing …. EF EnsureCreated verifies JUST the existence of the database not of the tables within)
So thats why I prefer WithEnvironment rather than .WithReference(rb.AddDatabase

Andrei Ignat weekly software news(mostly .NET)

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