Scott Hanselman

dotnet new worker - Windows Services or Linux systemd services in .NET Core

August 23, '19 Comments [9] Posted in DotNetCore | Open Source
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dotnet new workerYou've long been able to write Windows Services in .NET and .NET Core, and you could certainly write a vanilla Console App and cobble something together for a long running headless service as well. However, the idea of a Worker Process, especially a long running one is a core part of any operating system - Windows, Linux, or Mac.

Now that open source .NET Core is cross-platform, it's more than reasonable to want to write OS services in .NET Core. You might write a Windows Service with .NET Core or a systemd process for Linux with it as well.

Go grab a copy of .NET Core 3.0 - as of the time of this writing it's very close to release, and Preview 8 is supported in Production.

If you're making a Windows Service, you can use the Microsoft.Extensions.Hosting.WindowsService package and tell your new Worker that its lifetime is based on ServiceBase.

public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.UseWindowsService()
.ConfigureServices(services =>
{
services.AddHostedService<Worker>();
});

If you're making a Linux worker and using systemd you'd add the Microsoft.Extensions.Hosting.Systemd package and tell your new Worker that its lifetime is managed by systemd!

public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.UseSystemd()
.ConfigureServices((hostContext, services) =>
{
services.AddHostedService<Worker>();
});

The Worker template in .NET Core makes all this super easy and familiar if you're used to using .NET already. For example, logging is built in and regular .NET log levels like LogLevel.Debug or LogLevel.Critical are automatically mapped to systemd levels like Debug and Crit so I could run something like sudo journalctl -p 3 -u testapp and see my app's logs, just alike any other Linux process because it is!

You'll notice that a Worker doesn't look like a Console App. It has a Main but your work is done in a Worker class. A hosted service or services is added with AddHostedService and then a lot of work is abstracted away from you. The Worker template and BackgroundService base class brings a lot of the useful conveniences you're used to from ASP.NET over to your Worker Service. You get dependency injection, logging, process lifetime management as seen above, etc, for free!

public class Worker : BackgroundService
{
private readonly ILogger<Worker> _logger;

public Worker(ILogger<Worker> logger)
{
_logger = logger;
}

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
_logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
await Task.Delay(1000, stoppingToken);
}
}
}

This is a very useful template and it's available from the command line as "dotnet new worker" or from File New Project in Visual Studio 2019 Preview channel.

Also check out Brady Gaster's excellent blog post on running .NET Core workers in containers in Azure Container Instances (ACI). This is super useful if you have some .NET Core and you want to Do A Thing in the cloud but you also want per-second billing for your container.


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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SharpScript from ServiceStack lets you run .NET apps directly from a GitHub Gist!

August 15, '19 Comments [10] Posted in DotNetCore | Open Source
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I've blogged about ServiceStack before. It's an extraordinary open source project - an ecosystem of its own even - that is designed to be an alternative to the WCF, ASP.NET MVC, and ASP.NET Web API frameworks. I enjoy it so much I even helped write its tagline "Thoughtfully architected, obscenely fast, thoroughly enjoyable web services for all"

ServiceStack is an easy drop-in that simplifies creating Web Services in any ASP.NET Web App, but also in Self Hosting Console Apps, Windows Services and even Windows and OSX Desktop Apps - supporting both .NET Framework and .NET Core. The easiest way to get started is to create a new project from a ServiceStack VS.NET Template.

ServiceStack has released a new and amazing project that is absolutely audacious in its scope and elegant in its integration with the open source .NET Core ecosystem - #Script (pronounced "sharp script.")

Scripts IN your app!

There are a number of .NET projects that simulate REPL's or allow basic scripting, like "dotnet script" as an example or ScriptCS but I'm deeply impressed with #Script. To start with, #Script is somewhat better suited for scripting than Razor and it doesn't require precompilation. #Script is appropriate for live documents or Email Templates for example.

Here's a basic example of embedding a ScriptContext in your app:

var context = new ScriptContext().Init();
var output = context.EvaluateScript("Time is now: {{ now | dateFormat('HH:mm:ss') }}");

Where ServiceStack's #Script really shines is its use of .NET Core Global Tools. They've nabbed two global tool names - web and app (sassy!) and allow one to create SharpApps. From their site:

Sharp Apps leverages #Script to develop entire content-rich, data-driven websites without needing to write any C#, compile projects or manually refresh pages - resulting in the easiest and fastest way to develop Web Apps in .NET!

The web tool is cross platform and the app global tool is great for Windows as it supports .NET Core Windows Desktop Apps.

Your app IS a script!

You can write interactive SharpScripts or SharpApps that uses Chromium as a host.

You can literally run a "desktop" app self contained from a GitHub Gist!

Sharp Apps can also be published to Gists where they can be run on-the-fly without installation, they're always up-to-date, have tiny footprints are fast to download and launch that can also run locally, off-line and cross-platform across Windows, macOS and Linux OS's.

There's also a "gallery" that maps short names to existing examples. So run "app open" to get a list, then "app open name" to run one. You can just "app open blog" and you're running a quick local blog.

SharpApps

Easy to develop and run

The global tools make SharpApp a complete dev and runtime experience because you can just run "app" in the source folder and as you make code changes the hot-reloader updates the site as you Ctrl-S (save) a file!

If you've got .NET Core SDK installed (it's super quick) then just grab the local tool here (app on Windows and web anywhere else):

dotnet tool install --global app

And if you have a existing .NET Core web app you can launch it and run it in a Chromium Embedded Framework (CEF) browser with "app foo.dll" Check out this example on how to make and run a .NET Core app on the Windows Desktop with #Script.

ServiceStack CEF App

Then you can make a shortcut and add it to to the desktop with

app shortcut Acme.dll

Slick!

Code in #Script is done in markdown ```code blocks, while in Razor it's @{ } but it does use mustache template style. Go try out some of their Starter Projects!

#Script and SharpApps is an extraordinary addition to the .NET Core ecosystem and I'm just touching the surface. Do check out their site at https://sharpscript.net.

What do you think?


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Dotnet Depends is a great text mode development utility made with Gui.cs

August 1, '19 Comments [10] Posted in DotNetCore | Open Source
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I love me some text mode. ASCII, ANSI, VT100. Keep your 3D accelerated ray traced graphics and give me a lovely emoji-based progress bar.

Miguel has a nice thing called Gui.cs and I bumped into it in an unexpected and lovely place. There are hundreds of great .NET Global Tools that you can install to make your development lifecycle smoother, and I was installing Martin Björkström's lovely "dotnet depends" tool (go give him a GitHub star now!)  like this:

dotnet tool install -g dotnet-depends

Then I headed over to my Windows Terminal (get it free in the Store) and ran "dotnet depends" on my main website's code and was greeted by this (don't sweat the line spacing, that's a Terminal bug that'll be fixed soon):

dotnet depends in the Windows Terminal

How nice is this! It's a fully featured dependency explorer but it's all in text mode and doesn't require me to use the mouse and take my hands of the keyboard. If I'm already deep into the terminal/text mode, this is a great example of a solid, useful tool.

But how hard was it to make? Surprisingly little as his code is very simple. This is a testament to how he used the API and how Miguel designed it. He's separated the UI and the Business Logic, of course. He does the analysis work and stores it in a graph variable.

Here they're setting up some panes for the (text mode) Windows:

Application.Init();

var top = new CustomWindow();

var left = new FrameView("Dependencies")
{
Width = Dim.Percent(50),
Height = Dim.Fill(1)
};
var right = new View()
{
X = Pos.Right(left),
Width = Dim.Fill(),
Height = Dim.Fill(1)
};

It's split in half at this point, with the left side staying  at 50%.

var orderedDependencyList = graph.Nodes.OrderBy(x => x.Id).ToImmutableList();
var dependenciesView = new ListView(orderedDependencyList)
{
CanFocus = true,
AllowsMarking = false
};
left.Add(dependenciesView);
var runtimeDependsView = new ListView(Array.Empty<Node>())
{
CanFocus = true,
AllowsMarking = false
};
runtimeDepends.Add(runtimeDependsView);
var packageDependsView = new ListView(Array.Empty<Node>())
{
CanFocus = true,
AllowsMarking = false
};
packageDepends.Add(packageDependsView);
var reverseDependsView = new ListView(Array.Empty<Node>())
{
CanFocus = true,
AllowsMarking = false
};
reverseDepends.Add(reverseDependsView);

right.Add(runtimeDepends, packageDepends, reverseDepends);
top.Add(left, right, helpText);
Application.Top.Add(top)

The right side gets three ListViews added to it and the left side gets the dependencies view. Top it off with some clean data binding to the views and an initial call to UpdateLists. Anytime the dependenciesView gets a SelectedChanged event we'll call UpdateLists again.

top.Dependencies = orderedDependencyList;
top.VisibleDependencies = orderedDependencyList;
top.DependenciesView = dependenciesView;

dependenciesView.SelectedItem = 0;
UpdateLists();

dependenciesView.SelectedChanged += UpdateLists;

Application.Run();

What's in update lists? Filtering code for that graph variable from before.

void UpdateLists()
{
var selectedNode = top.VisibleDependencies[dependenciesView.SelectedItem];

runtimeDependsView.SetSource(graph.Edges.Where(x => x.Start.Equals(selectedNode) && x.End is AssemblyReferenceNode)
.Select(x => x.End).ToImmutableList());
packageDependsView.SetSource(graph.Edges.Where(x => x.Start.Equals(selectedNode) && x.End is PackageReferenceNode)
.Select(x => $"{x.End}{(string.IsNullOrEmpty(x.Label) ? string.Empty : " (Wanted: " + x.Label + ")")}").ToImmutableList());
reverseDependsView.SetSource(graph.Edges.Where(x => x.End.Equals(selectedNode))
.Select(x => $"{x.Start}{(string.IsNullOrEmpty(x.Label) ? string.Empty : " (Wanted: " + x.Label + ")")}").ToImmutableList());
}

That's basically it and it's fast as heck. Probably to be expected from the folks that brought you Midnight Commander.

Are you working on any utilities or cool projects and might want to consider - gasp - text mode over a website?


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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System.Text.Json and new built-in JSON support in .NET Core

July 23, '19 Comments [10] Posted in ASP.NET | DotNetCore | Javascript
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In a world where JSON (JavaScript Object Notation) is everywhere it's long been somewhat frustrating that .NET didn't have built-in JSON support. JSON.NET is great and has served us well but it's remained a 3rd party dependency for basic stuff like an ASP.NET web site or a simple console app.

Back in 2018 plans were announced to move JSON into .NET Core 3.0 as an intrinsic supported feature, and while they're at it, get double the performance or more with Span<T> support and no memory allocations. ASP.NET in .NET Core 3.0 removes the JSON.NET dependency but still allows you to add it back in a single line if you'd like.

NOTE: This is all automatic and built in with .NET Core 3.0, but if you’re targeting .NET Standard or .NET Framework. Install the System.Text.Json NuGet package (make sure to include previews and install version 4.6.0-preview6.19303.8 or higher). In order to get the integration with ASP.NET Core, you must target .NET Core 3.0.

It's very clean as well. Here's a simple example.

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace verysmall
{
class WeatherForecast
{
public DateTimeOffset Date { get; set; }
public int TemperatureC { get; set; }
public string Summary { get; set; }
}

class Program
{
static void Main(string[] args)
{
var w = new WeatherForecast() { Date = DateTime.Now, TemperatureC = 30, Summary = "Hot" };
Console.WriteLine(JsonSerializer.Serialize<WeatherForecast>(w));
}
}
}

The default options result in minified JSON as well.

{"Date":"2019-07-27T00:58:17.9478427-07:00","TemperatureC":30,"Summary":"Hot"}      

Of course, when you're returning JSON from a Controller in ASP.NET it's all automatic and with .NET Core 3.0 it'll automatically use the new System.Text.Json unless you override it.

Here's an example where we pull out some fake Weather data (5 randomly created reports) and return the array.

[HttpGet]
public IEnumerable<WeatherForecast> Get()
{
var rng = new Random();
return Enumerable.Range(1, 5).Select(index => new WeatherForecast
{
Date = DateTime.Now.AddDays(index),
TemperatureC = rng.Next(-20, 55),
Summary = Summaries[rng.Next(Summaries.Length)]
})
.ToArray();
}

The application/json is used and JSON is returned by default. If the return type was just string, we'd get text/plain. Check out this YouTube video to learn more details about System.Text.Json works and how it was designed. I'm looking forward to working with it more!


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Installing PowerShell with one line as a .NET Core global tool

July 18, '19 Comments [4] Posted in DotNetCore | Open Source | PowerShell
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I'PowerShell Mascotm a huge fan of .NET Core global tools. I've done a podcast on Global Tools. Just like Node and other platform have globally tools that can be easily and quickly installed and then used in build scripts, CI/CD (Continuous Integration/Continuous Deployment) systems, or just general command line utilities, .NET Global Tools are easily made (by you!) and distributed via NuGet.

Some cool examples (and there are hundreds) are the "Try .NET" Workshop runner and creator that can you can use to make interactive documentation, or coverlet for code coverage. There's a great and growing list of .NET Core Global Tools on GitHub.

If you've got the .NET SDK installed you can try out a global tool just like this.

dotnet tool install -g dotnetsay

Then run this example with "dotnetsay," it's fun.

stepping back a moment, you may be familiar with PowerShell. It's a scripting language and a command line shell like Bash or DOS or the Windows Command Prompt. You may think of PowerShell as a tool for maintaining and managing Windows Servers.

However in recent years, PowerShell has gone cross platform and runs most anywhere. It's lightweight and has .NET Core at its, ahem, core. You can use PowerShell for scripting systems on any platform and if you're a .NET developer the team has made installing and immediately using PowerShell in scripts a one liner - which is genius. It's PowerShell as a .NET Global Tool.

Here's an example output from my system running Ubuntu. I just "dotnet tool install --global PowerShell."

$ dotnet --version
2.1.502
$ dotnet tool install --global PowerShell
You can invoke the tool using the following command: pwsh
Tool 'powershell' (version '6.2.2') was successfully installed.
$ pwsh
PowerShell 6.1.1
https://aka.ms/pscore6-docs
Type 'help' to get help.
PS /mnt/c/Users/Scott/Desktop>
exit

Here I've checked that I have .NET 2.x or above, then I install PowerShell. I can run scripts or I can drop into the interactive shell. Note the PS prompt and my current directory above.

In fact, PowerShell is so useful as a scripting language when combined with .NET Core that PowerShell has been included as a global tool within the .NET Core 3.0 Preview Docker images since Preview 4. This means you can use PowerShell lines/scripts inside Docker images.

FROM mcr.microsoft.com/dotnet/core/sdk:3.0
RUN pwsh -c Get-Date
RUN pwsh -c "Get-Module -ListAvailable | Select-Object -Property Name, Path"

Being able to easily install PowerShell as a global tool means you can count on it in your scripts, CI/CDs systems, or docker containers. It's also nice to be able to be able to use existing PowerShell scripts cross platform.

I'm impressed with this idea - installing PowerShell itself as a .NET Global Tool. Very clever and useful.


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.