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Why is HttpRepl unable to find an OpenAPI description? The command "ls" does not show available endpoints

I am working through the Microsoft Learn tutorials to "Create a web API with ASP.Net Core".
Under the heading, "Build and test the web API", at instruction (5) I am getting a response, "Unable to find an OpenAPI description".
For step (6) when executing the "ls" command I get the response, "No directory structure has been set, so there is nothing to list. Use the 'connect' command to set a directory structure based on an OpenAPI description". I have tried the "connect" command suggested here and have tried "dir" as an alternative to "ls".
I can successfully change directories in step (7) and execute the GET request for step (8) and receive the expected reply. However, it really bothers me the "ls" command is not working here and seems like an important function of the httprepl tool.
How can I get the "ls" command to work here or tell me why does it not work?
C:\Users\xxxx\source\repos\Learn\ContosoPizza>httprepl http://localhost:5000
(Disconnected)> connect http://localhost:5000
Using a base address of http://localhost:5000/
Unable to find an OpenAPI description
For detailed tool info, see https://aka.ms/http-repl-doc
http://localhost:5000/> ls
No directory structure has been set, so there is nothing to list. Use the "connect" command to set a directory structure based on an OpenAPI description.
http://localhost:5000/>
ADDED RESULTS OF SUGGESTIONS--
C:\Users\xxxx\source\repos\Learn\ContosoPizza>dotnet --version
3.1.412
C:\Users\xxxx\source\repos\Learn\ContosoPizza>dotnet add WebAPI.csproj package Swashbuckle.AspNetCore -v 5.6.3
Could not find project or directory `WebAPI.csproj`.
httprepl GitHub repo and MS Docs page

The solution for me was to simply trust localhost's SSL certification, which you can do with this command:
dotnet dev-certs https --trust
While doing the same Tutorial, a friend of mine noticed, that trusting the dev certificate, was already covered by the Tutorial, which I had overlooked doing the Tutorial myself. This is the official help site:
Trust the ASP.NET Core HTTPS development certificate on Windows and macOS.
Maybe this will still help someone with the same problem.

In step 5 HttpRepl emits the warning Unable to find an OpenAPI description, which means that it can't find the swagger endpoint, and therefore the ls command wont work.
I assume you are using VS Code and ASP.NET Core 5.0. Here is my output from running dotnet --version:
5.0.401
If we are using Visual Studio, then remember to enable swagger when you create the project - I am using Visual Studio 2019 to create the screenshot:
Specifying your OpenAPI description
To find out which endpoint to use, open the file Startup.cs and locate the code fragment that contains the text UseSwaggerUI. You should find this block of code:
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseSwagger();
app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "WebAPI v1"));
}
Use the endpoint you find and run the tool like this:
httprepl http://localhost:5000 --openapi /swagger/v1/swagger.json
If you do not find any references to swagger, then see None of the above worked, swagger isn't installed below, for how to install and configure swagger for your project.
Ignoring your environment
If specifying the Open API endpoint to use doesn't work, then you are not running your Web API in a development environment. So either use a development environment, or uncomment the if-statement while testing (to setup your environment for development, see Changing your environment below):
//if (env.IsDevelopment())
//{
app.UseDeveloperExceptionPage();
app.UseSwagger();
app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "WebAPI v1"));
//}
Remember to restore the code you uncommented, if any, before you deploy to production.
Changing your environment
The profile your Web API is using, is specified in the file Properties\launchSettings.json. Open the file and search for ASPNETCORE_ENVIRONMENT. Then change the instances you find to:
"ASPNETCORE_ENVIRONMENT": "Development"
If this doesn't work, or the instances were already set to "Development", it means that you are not using any of the profiles specified in your launch settings. If no profile is used, ASPNETCORE_ENVIRONMENT defaults to "Production". When using the dotnet run command, the --launch-profile parameter lets you specify which profile to use:
dotnet run --launch-profile "name_of_profile"
As a last resort you can set the environment variable ASPNETCORE_ENVIRONMENT in the shell you are using, before you run the command dotnet run:
Bash
export ASPNETCORE_ENVIRONMENT=Development
CMD
set ASPNETCORE_ENVIRONMENT=Development
PowerShell
$env:ASPNETCORE_ENVIRONMENT='Development'
Then run the application without a profile :
dotnet run --no-launch-profile
The default ports, when running without a profile, should be 5000 or 5001. But read the output from the command, to see which ports it assigns to your Web API.
Please note, if you use VS Code to run your project, that VS Code may also have created launch settings in the .vscode\launch.json. It depends on how you have configured VS Code and what you allow it to do. I found some older articles, that claim that some extensions for VS Code, may interfere with the launch settings, but they didn't specify which ones.
None of the above worked, swagger isn't installed
I none of the above worked, it means you don't have swagger installed. Install swagger for your project and when done, try again.
Package Installation
Open your project in VS Code and run the following command from the Integrated Terminal and replace WebAPI.csproj with the name of your own project file:
dotnet add WebAPI.csproj package Swashbuckle.AspNetCore -v 5.6.3
You can of course run the command from outside VS Code, with your project folder as the current working directory.
Add and configure Swagger middleware
Add the Swagger generator to the services collection in the Startup.ConfigureServices method, as the last statement in the method:
public void ConfigureServices(IServiceCollection services)
{
[... other code here ...]
// Register the Swagger generator, defining 1 or more Swagger documents
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new OpenApiInfo { Title = "WebAPI", Version = "v1" });
});
}
In the Startup.Configure method, enable the middleware for serving the generated JSON document and the Swagger UI, at the top of the method:
public void Configure(IApplicationBuilder app)
{
// Enable middleware to serve generated Swagger as a JSON endpoint.
app.UseSwagger();
// Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.),
// specifying the Swagger JSON endpoint.
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});
[... other code here for setting up routing and the like ...]
}
To learn more about setting up swagger, profiles and the environment
Get started with Swashbuckle and ASP.NET Core
Managing Production and Development Settings in ASP.NET Core
Use multiple environments in ASP.NET Core
ASP.NET Core web API documentation with Swagger / OpenAPI

I had faced same issue. I have solved it by following:
In Developer PowerShell(VS 2022), Run 'dotnet run' command.
Keep this powershell as it is.
Now open new PowerShell and run "httprepl https://localhost:{PORT}"
You should be able to run api now.

You must be connected to the web server through dotnet run.

Service Starts, but The Program does not Run

We've created a new hosted service using .NET Core 3.1 and the WorkerService template.
We want to run this service as a "Windows Service".
If I run the program manually using a Powershell shell, it runs fine with no problems.
So I then added it as a windows service. To do this, I followed these steps:
Added the Microsoft.Extensions.Hosting.WindowsServices package
Added the following to CreateHostBuilder:
public static IHostBuilder CreateHostBuilder(Serilog.ILogger logger, string[] args) =>
Host.CreateDefaultBuilder(args)
.UseWindowsService() // <-- added this line
.ConfigureAppConfiguration(configurationBuilder =>
{
configurationBuilder.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: true);
})
Published it to a folder (zipped it and copied to server).
Added it as a service:
PS C:\Windows\system32> sc.exe create MyService binpath= "C:\Program Files\Services\MyService.exe"
5. Opened the Services snap-in and started the service.
The snap-in shows that it has a status of "running".
However, the program does not seem to actually do anything. It is not logging anything, including the most basic "Starting up" log message.
I even added a Seq sink on the off-chance that there was an IO problem preventing it from writing to a file. But nothing.
Can anyone identify what I am doing wrong?

As per comment on issue 36065, when a .NET Core 3.1 worker service runs as a windows service "Directory.GetCurrentDirectory() will point to %WINDIR%\system32". Therefore to get the current directory, you could use some reflection and something like:
public static IHostBuilder CreateHostBuilder(Serilog.ILogger logger, string[] args) =>
Host.CreateDefaultBuilder(args)
.UseWindowsService() // <-- added this line
.ConfigureAppConfiguration(configurationBuilder =>
{
configurationBuilder.SetBasePath(Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location))
.AddJsonFile("appsettings.json", optional: true);
});
Worth noting, according to this comment, it's resolved in .NET 5.0

How to set ASPNETCORE_ENVIRONMENT for console application?

I have the following simple console application that contains a hosted service:
public static async Task Main(string[] args)
{
using (var host = Host.CreateDefaultBuilder(args)
.ConfigureServices((hostContext, services) =>
{
// db context
services.AddEntityFrameworkNpgsql()
.AddDbContext<ApplicationDbContext>();
// hosted services
services.AddHostedService<ConsumeScopedServiceHostedService>();
services.AddScoped<ProcessManuallySendings>();
// services
services.AddHttpClient<ISendPushService, SendPushService>(x
=>
{
x.Timeout = TimeSpan.FromSeconds(65);
});
})
.Build())
{
// Start the host
await host.StartAsync();
// Wait for the host to shutdown
await host.WaitForShutdownAsync();
}
}
}
It works with my database and it means that it requires connection string. I have three appsettings.json files:
On the development server I will use Development environment, on the production - Production. On my local machine I'm going to use Local. It's simple.
I'm going to get it with the help of ASPNETCORE_ENVIRONMENT (OS environment variable).
I use Linux and in my shell (zsh) config file I have:
When I type in my terminal $ echo $ASPNETCORE_ENVIRONMENT I have Local.
But when I start my console application
$ dotnet run // in the project folder
It's trying to start with Production environment.
See debug output:
So how to set environment? Why Os variable doesn't work?

According to the docs for .Net Core 3.0 onwards, the host configuration is provided from environment variables prefixed with DOTNET_ (for example, DOTNET_ENVIRONMENT).
If that doesn't work, you could also try setting the environment variable in the launchSettings.json like this on your profile.
"environmentVariables": {
"ASPNETCORE_ENVIRONMENT": "Development",
"DOTNET_ENVIRONMENT" : "Development"
}

With .NET Core 3, the generic host uses the DOTNET_ prefix, not the old ASPNETCORE_ prefix.

When setting environment variables in rider for a console application in dotnet core 3.1, neither ASPNETCORE_ENVIRONMENT nor DOTNET_ENVIRONMENT worked regardless of whether they were set in the Run/Debug Configuration or LaunchSettings.
In my situation, I am using Microsoft.Extensions.Hosting and Microsoft.Extensions.Hosting.Abstractions and wanted hostEnvironment to be resolved correctly to Development.
if (hostEnvironment.IsDevelopment())
{
optionsBuilder.EnableSensitiveDataLogging();
optionsBuilder.AddInterceptors(new EfCommandInterceptor());
}
To get this working, I had to create an environment variable called ENVIRONMENT with the appropriate value.
ENVIRONMENT=Development

How to set hosting environment name for .NET Core console app using Generic Host (HostBuilder)

I am setting up a .NET Core 2.x console app as a Windows service and need to load an appsettings json file based on the environment. I was thinking to start the service with a command line argument that identifies the environment. How can I do that in Visual Studio? No matter what I set in the project settings, the EnvironmentName value is always "Production".
How can I set my environment from a command line argument?
var hostBuilder = new HostBuilder()
.UseContentRoot(Directory.GetCurrentDirectory())
.ConfigureAppConfiguration((hostingContext, config) =>
{
var env = hostingContext.HostingEnvironment;
config.AddCommandLine(args);
config.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: false, reloadOnChange: true);
config.AddEnvironmentVariables();
})
.ConfigureServices((hostContext, services) =>
{
//Inject additional services as needed
services.AddHostedService<JobRunner>();
});

You can set the environment from the command line variables via the ConfigureHostConfiguration extension method.
Set up the configuration for the builder itself. This will be used to
initialize the Microsoft.Extensions.Hosting.IHostEnvironment for use
later in the build process.
var hostBuilder = new HostBuilder()
.UseContentRoot(Directory.GetCurrentDirectory())
.ConfigureHostConfiguration(configurationBuilder => {
configurationBuilder.AddCommandLine(args);
})
.ConfigureAppConfiguration((hostingContext, cfg) =>
{
// ...
var env = hostingContext.HostingEnvironment;
Console.WriteLine(env.EnvironmentName); // Test
// ...
});
// ...
hostBuilder.Build();
In Visual Studio, you configure the application arguments with the same ones as being used by dotnet run which is --environment,
e.g. dotnet run --environment Test.
Without this application argument, the hosting environment defaults back to Production.

In Visual Studio, you can add an environment variable under the Debug tab of the console application properties. For a console application the environment variable provider name must be prefixed by DOTNET_ for the generic host builder to recognize it. In this case, the provider name is DOTNET_ENVIRONMENT.
If this provider name is not specified, the default is Production.
Reference : https://learn.microsoft.com/en-us/aspnet/core/fundamentals/host/generic-host?view=aspnetcore-5.0#host-configuration

Another method is to use the "UseEnvironnement" method directly on the host builder :
https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.hosting.hostinghostbuilderextensions.useenvironment?view=dotnet-plat-ext-5.0
For example :
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.UseEnvironment("dev") // Magic is here
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseUrls("http://0.0.0.0:8081");
webBuilder.UseStartup<Startup>();
});

To add to pfx's accepted answer above, in Visual studio 2022, the environment variable can be set either via Properties window in UI:
or set the environment variable:
or directly edit the launchSettings.json file under Properties and add command line arguement:

If you are using Visual Studio 2022 with .Net 5, the UI could be a bit overwhelming. Its simple to edit launchSettings.json file under properties.
Mine looks as follows. Note its DOTNET_ENVIRONMENT and NOT ASPNETCORE_ENVIRONMENT for .NET Core console app using Generic Host (HostBuilder)
{
"profiles": {
"Bvh.HrSita.DbMigrator": {
"commandName": "Project",
"environmentVariables": {
"DOTNET_ENVIRONMENT": "Development"
}
},
"Bvh.HrSita.DbMigrator.Prod": {
"commandName": "Project",
"environmentVariables": {
"DOTNET_ENVIRONMENT": "Production"
}
},
"Bvh.HrSita.DbMigrator.Stag": {
"commandName": "Project",
"environmentVariables": {
"DOTNET_ENVIRONMENT": "Staging"
}
},
"Docker": {
"commandName": "Docker"
}
}
}
Now select what ever profile you want when you launch the project. The following shows it all along with Program.cs.
And finally if you are trying to run the same in an Azure DevOps pipeline, the task should be as shown below. The arguments should have --environment Production. Note that adding env: is somehow NOT working for me as suggested here.
- task: DotNetCoreCLI#2
displayName: 'Run DbMigrator Project on the newly provisoned database'
inputs:
command: run
projects: '$(Pipeline.Workspace)/$(finalBuildArtifactName)/src/Bvh.HrSita.DbMigrator/Bvh.HrSita.DbMigrator.csproj'
arguments: '--configuration $(BuildConfiguration) --environment Production'
env:
DOTNET_ENVIRONMENT: Production

To pick up the hosting environment from environment variables, you can also add:
.ConfigureHostConfiguration(config =>
{
config.AddEnvironmentVariables();
})
Then use Environment environment variable to pass the actual environment.

If you are using visual studio and you have project configuration (Debug, Release, CustomUser...)
then you could include appsettings.[config-name].json like this:
Host
.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((context, builder) => {
//add visual studio configuration manager
builder.AddJsonFile($"appSettings.{Assembly.GetExecutingAssembly().GetCustomAttribute<AssemblyConfigurationAttribute>().Configuration}.json", true);
...
})
...

In Visual Studio 2022 and .NET 6.0, appsettings.json and appsettings.[EnvironmentName].json are automatically included in configuration sources when using HostBuilder:
So there is no need to manually add these in ConfigureServices.
You still need to set EnvironmentName in launchSettings.json or as a commandline argument as shown in the other answers.

I run into this issue time and time again and can never remember what my solution was from the previous time I ran into it. Typically, I'm simply trying to get a Development and Production environment in my console app like you get by default with a web app (configured with launchSettings.json and other more buried mechanisms).
At the beginning of my Program.cs in my console app, I add:
#if DEBUG
Environment.SetEnvironmentVariable("DOTNET_ENVIRONMENT", "Development");
#endif
var env = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT") ?? "Production";
Console.WriteLine($"{env}");
However, you could also just as easily define your environment outright with the debug condition:
var env = "Production";
#if DEBUG
env = "Development";
#endif
Console.WriteLine($"{env}");
You can also set your EnvironmentName like this:
var host = Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((context, config) =>
{
#if DEBUG
context.HostingEnvironment.EnvironmentName = "Development";
#endif
var env = context.HostingEnvironment.EnvironmentName;
Console.WriteLine(env);
config.AddJsonFile("appsettings.json", optional: true)
.AddJsonFile($"appsettings.{env}.json", optional: true);
}).Build();
It's not command line, but should work as a solution. I also rarely see this suggested and found this digging through one of my older projects (after hours of searching online), so I'm not sure if it has any downsides (other than mostly only being good for one other environment besides Production)? Please leave a comment if there are other gotchas. It's definitely the easiest to implement for a console app.
Part of the reason for posting this answer also is so my future self can hopefully find it more quickly than this time around.

Cannot find module 'aspnet-webpack' when using 'dotnet publish' in .Net Core 2.0 & Angular

I have been trying to follow answers to this problem but to no avail.. I am trying to publish my .Net Core 2.0 & Angular project using the command line command 'dotnet publish' I successfully publish, however when trying to run my project's .dll in the published folder, my project spits in out this error when run in a development environment:
Unhandled Exception: System.AggregateException: One or more errors occurred. (Webpack dev middleware failed because of an error while loading 'aspnet-webpack'. Error was: Error: Cannot find module 'aspnet-webpack'
When run in Production and allowing for the DeveloperExceptionPage (as shown in my statup.cs below) the .netcore app runs, but crashes within the actual web app, which I assume is due to the larger error, aspnet-webpack not being found:
NodeInvocationException: Uncaught (in promise): Error: No component factory found for HomeComponent. Did you add it to #NgModule.entryComponents?
Startup.cs
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
}
// 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.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions
{
HotModuleReplacement = true
});
}
else
{
//app.UseExceptionHandler("/Home/Error");
app.UseDeveloperExceptionPage();
}
app.UseStaticFiles();
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
routes.MapSpaFallbackRoute(
name: "spa-fallback",
defaults: new { controller = "Home", action = "Index" });
});
}
}
I am not using #Angular/Cli, but I am using the default Angular Project that VS2017 (August update, I believe?) generates, which seems to only use Webpack. The problem seems to be that the Production config of the project expects a reference that I am not providing, but I can not figure out why that is.
No other answers to this question have helped me thus far, so I apologize if this is a repeat question.

After you publish your .Net Core 2.0 & Angular project, and before you run it, you need to ensure that the environment variable ASPNETCORE_ENVIRONMENT isn't set to Development. The published project doesn't include support for the WebpackDevMiddleware or HotModuleReplacement. But it will attempt to use them if the environment is set to Development.
HotModuleReplacement automatically updates Webpack-built resources (such as JavaScript, CSS, or images) in your web browser whenever source files are changed. This is obviously something that you don't want in production.
If ASPNETCORE_ENVIRONMENT is set to "Development", you can change the setting with:
setx ASPNETCORE_ENVIRONMENT "Production"
You will need to close the current command window and open another to see the change.
You can also comment out the following code in startup.cs to accomplish the same result:
#if DEBUG
app.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions
{
HotModuleReplacement = true
});
#endif

Make sure you have fully installed all of these dependencies:
npm install webpack-hot-middleware --save-dev
npm install webpack-dev-middleware --save-dev
npm install aspnet-webpack --save-dev

In my case the cause was that the SPA (Vue in my case) is in the ClientApp folder and app.UseWebpackDevMiddleware expects it to be in the project root.
Setting the ProjectPath option solved this for me.
app.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions
{
HotModuleReplacement = true,
ConfigFile = Path.Combine(env.ContentRootPath, #"ClientApp\node_modules\#vue\cli-service\webpack.config.js"),
ProjectPath = Path.Combine(env.ContentRootPath, #"ClientApp")
});

I had same issue with "aspnet-webpack", this was introduced halfway in the project development so I was bit surprised to see sudden death of the solution. It was all working fine couple of months on IIS but suddenly failed to boot.
IIS log files were not helpful, so I tried to resolve this couple of ways, one of them worked. Hurry!
Solution
I ran following on package-manager window :
dotnet run --project <Full path of *.csproj> --configuration Debug
It give me some pointers and I started searching for "Error: Cannot find module 'aspnet-webpack'" issue. I tried to go through all the changes for last couple of check-ins, and found out that we updated the "Microsoft.AspNetCore.All" from 2.0.0 to 2.0.3 version, so downgrading it to original version fixed it.
I guess they both uses different versions of node packages. So don't update for sake unless for a very good reason. Reading around this some bits are very tightly coupled to specific versions and Angular very easily breaks, if something changed. In process though I have managed to upgrade the node version to latest 5.0.0
Love to find more details, but for time being no details on why it needs a specific version.

I got the same error as you in a project without Angular:
Unhandled Exception: System.AggregateException: One or more errors occurred. (Webpack dev middleware failed because of an error while loading 'aspnet-webpack'. Error was: Error: Cannot find module 'aspnet-webpack'
Turned out to be a simple problem with node that I tend to forget.
npm install
Remember that npm commands need to be run in the top directory which contains your package.json file. I hope that this helps someone who has as much problems as me remembering to actually run npm commands. Thanks to the forum which reminded me:
https://www.ebenmonney.com/forum/?view=thread&id=20&part=1#postid-57

Check that node.js is installed in production and is in the path.
Node.js is used by webpack
Also check that you have a recent version of Node.js (4+)
Reference : AspNetCore + Angular 2: WebpackDevMiddleware Error with new project
Version of Node.js can be checked with :
where.exe node.exe (Windows 7+)
which node.exe (linux bash)
And of course path environment variable should be checked and updated if pointing to obsolete Node.js
All the best

AT configure function of startup.cs You can use if statement for development environment
if (env.IsDevelopment())
{
// Print exception and all details for the developer
app.UseDeveloperExceptionPage();
// Use WebPack to update css , js , html automatically
app.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions
{
HotModuleReplacement = true
});
}
else
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
You can this comman in command print to change current environment :
setx ASPNETCORE_ENVIRONMENT "Development"

The main reason for this error is that you are using a dependency somewhere in your code and it isn't installed in your solution. If you are using visual studio, try using clean build, it will show up the errors in your project which'll help you in finding it.