Scott Hanselman

In May of last year doing things with ASP.NET and Docker was in its infancy. But cool stuff was afoot. I wrote a blog post showing how to publish an ASP.NET 5 (5 at the time, now Core 1.0) app to Docker. Later in December of 2015 new tools like Docker Toolbox and Kitematic made things even easier. In May of 2016 Docker for Windows Beta continued to move the ball forward nicely.

I wanted to see how things are looking with ASP.NET Core, Docker, and Windows here in October of 2016.

I installed these things:

• Visual Studio Community 2015
  • Visual Studio 2015 Update 3
• ASP.NET Core with .NET Core
  • .NET Core 1.0.1 - VS 2015 Tooling Preview 2
• Docker for Windows (I used the Beta Channel)
• Visual Studio Tools for Docker

Docker for Windows is really nice as it automates setting up Hyper-V for you and creates the Docker host OS and gets it all running. This is a big time saver.

There's my Linux host that I don't really have to think about. I'll do everything from the command line or from Visual Studio.

I'll say File | New Project and make a new ASP.NET Core application running on .NET Core.

Then I right click and Add | Docker Support. This menu comes from the Visual Studio Tools for Docker extension. This adds a basic Dockerfile and some docker-compose files. Out of the box, I'm all setup to deploy my ASP.NET Core app to a Docker Linux container.

ASP.NET Core in a Docker Linux Container

Starting from my ASP.NET Core app, I'll make sure my base image (that's the FROM in the Dockerfile) is the base ASP.NET Core image for Linux.

FROM microsoft/aspnetcore:1.0.1
ENTRYPOINT ["dotnet", "WebApplication4.dll"]
ARG source=.
WORKDIR /app
EXPOSE 80
COPY $source .

Next, since I don't want Docker to do the building of my application yet, I'll publish it locally. Be sure to read Steve Lasker's blog post "Building Optimized Docker Images with ASP.NET Core" to learn how to have one docker container build your app and the other run it it. This optimizes server density and resource.

I'll publish, then build the images, and run it.

>dotnet publish

>docker build bin\Debug\netcoreapp1.0\publish -t aspnetcoreonlinux 

>docker images
REPOSITORY             TAG                 IMAGE ID            CREATED             SIZE
aspnetcoreonlinux      latest              dab2bff7e4a6        28 seconds ago      276.2 MB
microsoft/aspnetcore   1.0.1               2e781d03cb22        44 hours ago        266.7 MB

>docker run -it -d -p 85:80 aspnetcoreonlinux
1cfcc8e8e7d4e6257995f8b64505ce25ae80e05fe1962d4312b2e2fe33420413

>docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                NAMES
1cfcc8e8e7d4        aspnetcoreonlinux   "dotnet WebApplicatio"   2 seconds ago       Up 1 seconds        0.0.0.0:85->80/tcp   clever_archimedes

And there's my ASP.NET Core app running in Docker. So I'm running Windows, running Hyper-V, running a Linux host that is hosting Docker containers.

What else can I do?

ASP.NET Core in a Docker Windows Container running Windows Nano Server

There's Windows Server, there's Windows Server Core that removes the UI among other things and there's Windows Nano Server which gets Windows down to like hundreds of megs instead of many gigs. This means there's a lot of great choices depending on what you need for functionality and server density. Ship as little as possible.

Let me see if I can get ASP.NET Core running on Kestrel under Windows Nano Server. Certainly, since Nano is very capable, I could run IIS within the container and there's docs on that.

Michael Friis from Docker has a great blog post on building and running your first Docker Windows Server Container. With the new Docker for Windows you can just right click on it and switch between Linux and Windows Containers.

So now I'm using Docker with Windows Containers. You may not know that you likely already have Windows Containers! It was shipped inside Windows 10 Anniversary Edition. You can check for Containers in Features:

I'll change my Dockerfile to use the Windows Nano Server image. I can also control the ports that ASP.NET talks on if I like with an Environment Variable and Expose that within Docker.

FROM microsoft/dotnet:nanoserver
ENTRYPOINT ["dotnet", "WebApplication4.dll"]
ARG source=.
WORKDIR /app
ENV ASPNETCORE_URLS http://+:82
EXPOSE 82
COPY $source .

Then I'll publish and build...

>dotnet publish
>docker build bin\Debug\netcoreapp1.0\publish -t aspnetcoreonnano 

Then I'll run it, mapping the ports from Windows outside to the Windows container inside!

NOTE: There's a bug as of this writing that affects how Windows 10 talks to Containers via "NAT" (Network Address Translation) such that you can't easily go http://localhost:82 like you (and I) want to. Today you have to hit the IP of the container directly. I'll report back once I hear more about this bug and how it gets fixed. It'll show up in Windows Update one day. The workaround is to get the IP address of the container from docker like this:  docker inspect -f "{{ .NetworkSettings.Networks.nat.IPAddress }}" HASH

UPDATE: This bug has been fixed in the Windows 10 April Update. Details here Localhost Access to Windows Container Ports

So I'll run my ASP.NET Core app on Windows Nano Server (again, to be clear, this is running on Windows 10 and Nano Server is inside a Container!)

>docker run -it -d -p 88:82 aspnetcoreonnano
afafdbead8b04205841a81d974545f033dcc9ba7f761ff7e6cc0ec8f3ecce215

>docker inspect -f "{{ .NetworkSettings.Networks.nat.IPAddress }}" afa
172.16.240.197

Now I can hit that site with 172.16.240.197:82. Once that bug above is fixed, it'll get hit and routed like any container.

The best part about Windows Containers is that they are fast and lightweight. Once the image is downloaded and build on your machine, you're starting and stopping them in seconds with Docker.

BUT, you can also isolate Windows Containers using Docker like this:

docker run --isolation=hyperv -it -d -p 86:82 aspnetcoreonnano

So now this instance is running fully isolated within Hyper-V itself. You get the best of all worlds. Speed and convenient deployment plus optional and easy isolation.

ASP.NET Core in a Docker Windows Container running Windows Server Core 2016

I can then change the Dockerfile to use the full Windows Server Core image. This is 8 gigs so be ready as it'll take a bit to download and extract but it is really Windows. You can also choose to run this as a container or as an isolated Hyper-V container.

Here I just change the FROM to get a Windows Sever Core with .NET Core included.

FROM microsoft/dotnet:1.0.0-preview2-windowsservercore-sdk
ENTRYPOINT ["dotnet", "WebApplication4.dll"]
ARG source=.
WORKDIR /app
ENV ASPNETCORE_URLS http://+:82
EXPOSE 82
COPY $source .

NOTE: I hear it's likely that the the .NET Core on Windows Server Core images will likely go away. It makes more sense for .NET Core to run on Windows Nano Server or other lightweight images. You'll use Server Core for heavier stuff, and Server is nice because it means you can run "full" .NET Framework apps in containers! If you REALLY want to have .NET Core on Server Core you can make your own Dockerfile and easily build and image that has the things you want.

Then I'll publish, build, and run again.

>docker images
REPOSITORY             TAG                                    IMAGE ID            CREATED             SIZE
aspnetcoreonnano       latest                                 7e02d6800acf        24 minutes ago      1.113 GB
aspnetcoreonservercore latest                                 a11d9a9ba0c2        28 minutes ago      7.751 GB

Since containers are so fast to start and stop I can have a complete web farm running with Redis in a Container, SQL in another, and my web stack in a third. Or mix and match.

>docker ps
CONTAINER ID        IMAGE                 COMMAND                  PORTS                NAMES
d32a981ceabb        aspnetcoreonwindows   "dotnet WebApplicatio"   0.0.0.0:87->82/tcp   compassionate_blackwell
a179a48ca9f6        aspnetcoreonnano      "dotnet WebApplicatio"   0.0.0.0:86->82/tcp   determined_stallman
170a8afa1b8b        aspnetcoreonnano      "dotnet WebApplicatio"   0.0.0.0:89->82/tcp   agitated_northcutt
afafdbead8b0        aspnetcoreonnano      "dotnet WebApplicatio"   0.0.0.0:88->82/tcp   naughty_ramanujan
2cf45ea2f008        a7fa77b6f1d4          "dotnet WebApplicatio"   0.0.0.0:97->82/tcp   sleepy_hodgkin

Conclusion

Again, go check out Michael's article where he uses Docker Compose to bring up the ASP.NET Music Store sample with SQL Express in one Windows Container and ASP.NET Core in another as well as Steve Lasker's blog (in fact his whole blog is gold) on making optimized Docker images with ASP.NET Core.

IMAGE ID            RESPOSITORY                   TAG                 SIZE
0ec4274c5571        web                          optimized           276.2 MB
f9f196304c95        web                          single              583.8 MB
f450043e0a44        microsoft/aspnetcore         1.0.1               266.7 MB
706045865622        microsoft/aspnetcore-build   1.0.1               896.6 MB

Steve points out a number of techniques that will allow you to get the most out of Docker and ASP.NET Core.

The result of all this means (IMHO) that you can use ASP.NET Core:

• ASP.NET Core on Linux
  • within Docker containers
  • in any Cloud
• ASP.NET Core on Windows, Windows Server, Server Core, and Nano Server.
  • within Docker windows containers
  • within Docker isolated Hyper-V containers

This means you can choose the level of feature support and size to optimize for server density and convenience. Once all the tooling (the Docker folks with Docker for Windows and the VS folks with Visual Studio Docker Tools) is baked, we'll have nice debugging and workflows from dev to production.

What have you been doing with Docker, Containers, and ASP.NET Core? Sound off in the comments.

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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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I had a reader send me a question yesterday. She basically wanted to use her existing .NET Framework libraries in an ASP.NET Core application, and it wasn't super clear how to do it.

I have a quick question for you regarding asp.net core. We are rewriting our website using asp.net core, empty from the bottom up. We have 2 libraries written in .net 4.6 . One is our database model and repositories and the other is a project of internal utilities we use a lot. Unfortunately we cannot see how to reference these two projects in our .net core project.

It can be a little confusing. As I mentioned earlier this week, some people don't realize that ASP.NET Core 1.0 (that's the web framework bit) runs on either .NET Core or .NET Framework 4.6 aka "Full Framework."

When you make a new web project in Visual Studio you see (today) this dialog. Note in the dropdown at the top you can select your minimum .NET Framework version. You can select 4.6.2, if you like, but I'll do 4.5.2 to be a little more compatible. It's up to you.

This dialog could use clearer text and hopefully it will soon.

• There's the regular ASP.NET Web Application at the top. That's ASP.NET 4.6 with MVC and Web API. It runs on the .NET Framework.
• There's ASP.NET Core 1.0 running on .NET Core. That's cross platform. If you select that one you'll be able to run your app anywhere but you can't reference "Full" .NET Framework assemblies as they are just for Windows.  If you want to run anywhere you need to use .NET Standard APIs that will run anywhere.
• There's ASP.NET Core 1.0 running on .NET Framework. That's the new ASP.NET Core 1.0 with unified MVC and Web API but running on the .NET Framework you run today on Windows.

As we see in the diagram above, ASP.NET Core 1.0 is the new streamlined ASP.NET  that can run on top of both .NET Framework (Windows) and .NET Core (Mac/Windows/Linux).

I'll chose ASP.NET Core on .NET Framework and I'll see this in my Solution Explorer:

I've got another DLL that I made with the regular File | New Project | Class Library.

Then I reference it the usual way with Add Reference and it looks like this in the References node in Solution Explorer. Note the icon differences.

If we look in the project.json (Be aware that this will change for the better in the future when project.json's functionality is merged with csproj and msbuild) you'll note that the ClassLIbrary1 isn't listed under the top level dependencies node, but as a framework specific dependency like this:

{
  "dependencies": {
    "Microsoft.StuffAndThings": "1.0.0",
    "Microsoft.AspNetCore.Mvc": "1.0.1",
  },

  "frameworks": {
    "net452": {
      "dependencies": {
        "ClassLibrary1": {
          "target": "project"
        }
      }
    }
  }
}

Notice also that in this case it's a type="project" dependency in this case as I didn't build a NuGet package and reference that.

Since the .NET Core tooling is in preview there are some gotchas when doing this today.

• Make sure that all your class libraries are targeting an appropriate version of the .NET Framework.
• For example, don't have a 4.5.2 Web App targeting a 4.6.2 Class Library. This could bite you in subtle ways if things don't line up in production.
• dotnet restore at the command line may well get confused and give you an error like:
• Errors in D:\github\WebApplication2\src\WebApplication2\project.json - Unable to resolve 'ClassLibrary1' for '.NETFramework,Version=v4.5.2'.
• Use Visual Studio to build or run msbuild at the command line.
• You can restore packages from the command line with nuget.exe version 3.4.4 or greater if you restore on the .sln file like this:
• D:\github\WebApplication2>nuget restore WebApplication2.sln
  MSBuild auto-detection: using msbuild version '14.0' from 'C:\Program Files (x86)\MSBuild\14.0\bin'.
• I recommend you run nuget.exe to see what version you have and run nuget update -self to have it update itself.
• You can also download specific NuGet versions at https://dist.nuget.org/index.html

These gotchas will be fixed when the tooling is finalized.

Hope this helps!

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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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ASP.NET Core 1.0 is out, as is .NET Core 1.0 and lots of folks are making great cross-platform web apps. These are Web Apps that are built on .NET Core 1.0 and run on Windows, Mac, or Linux.

However, some people don't realize that ASP.NET Core 1.0 (that's the web framework bit) runs on either .NET Core or .NET Framework 4.6 aka "Full Framework."

Once you realize that it can be somewhat liberating. If you want to check out the new ASP.NET Core 1.0 and use the unified controllers to make web apis or MVC apps with Razor you can...even if you don't need or care about cross-platform support. Maybe your libraries use COM objects or Windows-specific stuff. ASP.NET Core 1.0 works on .NET Framework 4.6 just fine.

Another option that folks don't consider when talk of "porting" their apps comes up at work is - why not have two apps? There's no reason to start a big porting exercise if your app works great now. Consider that you can have a section of your site by on ASP.NET Core 1.0 and another be on ASP.NET 4.x and the two apps could share authentication cookies. The user would never know the difference.

Barry Dorrans from our team looked into this, and here's what he found. He's interested in your feedback, so be sure to file issues on his GitHub Repo with your thoughts, bugs, and comments. This is a work in progress and at some point will be updated into the official documentation.

Sharing Authorization Cookies between ASP.NET 4.x and .NET Core

Barry is building a GitHub repro here with two sample apps and a markdown file to illustrate clearly how to accomplish cookie sharing.

When you want to share logins with an existing ASP.NET 4.x app and an ASP.NET Core 1.0 app, you'll be creating a login cookie that can be read by both applications. It's certainly possible for you, Dear Reader, to "hack something together" with sessions and your own custom cookies, but please let this blog post and Barry's project be a warning. Don't roll your own crypto. You don't want to accidentally open up one or both if your apps to hacking because you tried to extend auth/auth in a naïve way.

First, you'll need to make sure each application has the right NuGet packages to interop with the security tokens you'll be using in your cookies.

Install the interop packages into your applications.

1. ASP.NET 4.5

   Open the nuget package manager, or the nuget console and add a reference to Microsoft.Owin.Security.Interop.

2. ASP.NET Core

   Open the nuget package manager, or the nuget console and add a reference to Microsoft.AspNetCore.DataProtection.Extensions.

Make sure the Cookie Names are identical in each application

Barry is using CookieName = ".AspNet.SharedCookie" in the example, but you just need to make sure they match.

services.AddIdentity<ApplicationUser, IdentityRole>(options =>
{
    options.Cookies = new Microsoft.AspNetCore.Identity.IdentityCookieOptions
    {
        ApplicationCookie = new CookieAuthenticationOptions
        {
            AuthenticationScheme = "Cookie",
            LoginPath = new PathString("/Account/Login/"),
            AccessDeniedPath = new PathString("/Account/Forbidden/"),
            AutomaticAuthenticate = true,
            AutomaticChallenge = true,
            CookieName = ".AspNet.SharedCookie"

        };
    })
    .AddEntityFrameworkStores<ApplicationDbContext>()
    .AddDefaultTokenProviders();
}

Remember the CookieName property must have the same value in each application, and the AuthenticationType (ASP.NET 4.5) and AuthenticationScheme (ASP.NET Core) properties must have the same value in each application.

Be aware of your cookie domains if you use them

Browsers naturally share cookies between the same domain name. For example if both your sites run in subdirectories under https://contoso.com then cookies will automatically be shared.

However if your sites run on subdomains a cookie issued to a subdomain will not automatically be sent by the browser to a different subdomain, for example, https://site1.contoso.com would not share cookies with https://site2.contoso.com.

If your sites run on subdomains you can configure the issued cookies to be shared by setting the CookieDomain property in CookieAuthenticationOptions to be the parent domain.

Try to do everything over HTTPS and be aware that if a Cookie has its Secure flag set it won't flow to an insecure HTTP URL.

Select a common data protection repository location accessible by both applications

From Barry's instructions, his sample will use a shared DP folder, but you have options:

This sample will use a shared directory (C:\keyring). If your applications aren't on the same server, or can't access the same NTFS share you can use other keyring repositories.

.NET Core 1.0 includes key ring repositories for shared directories and the registry.

.NET Core 1.1 will add support for Redis, Azure Blob Storage and Azure Key Vault.

You can develop your own key ring repository by implementing the IXmlRepository interface.

Configure your applications to use the same cookie format

You'll configure each app - ASP.NET 4.5 and ASP.NET Core - to use the AspNetTicketDataFormat for their cookies.

According to his repo, this gets us started with Cookie Sharing for Identity, but there still needs to be clearer guidance on how share the Identity 3.0 database between the two frameworks.

The interop shim does not enabling the sharing of identity databases between applications. ASP.NET 4.5 uses Identity 1.0 or 2.0, ASP.NET Core uses Identity 3.0. If you want to share databases you must update the ASP.NET Identity 2.0 applications to use the ASP.NET Identity 3.0 schemas. If you are upgrading from Identity 1.0 you should migrate to Identity 2.0 first, rather than try to go directly to 3.0.

Sound off in the Issues over on GitHub if you would like to see this sample (or another) expanded to show more Identity DB sharing. It looks to be very promising work.

Sponsor: Big thanks to Telerik for sponsoring the blog this week! 60+ ASP.NET Core controls for every need. The most complete UI toolset for x-platform responsive web and cloud development.Try now 30 days for free!

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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It's official. I'm a better programmer when I'm pairing with someone. Pair Programming (two people, one keyboard) has been around for at least 20+ years, if not much longer. Usually one person types while another person (paces around and) thinks. It is kind of a "driver and navigator" model.

Everyone is different, to be clear, so it's very possible that you are the kind of person who can disappear into a closet for 8 hours and emerge with code, triumphant. I've done this before. Some of my best projects have involved me coding alone and that's fine.

However, just has we know that "diverse teams make for better projects," the same is true in my experience when coding on specific problems. Diversity isn't just color and gender, etc, it's as much background, age, personal history, work experience, expertise, programming language of choice, heck, it's even google-ability, and more!

How many times have you banged your head against a wall while coding only to have a friend or co-worker find the answer on their first web search?

Good pair programming is like that. Those ah-ha moments happen more often and you'll feel more than twice as productive in a pair.

In fact, I'm trying to pair for an hour every week remotely. Mark Downie and I have been pairing on DasBlog on and off for a year or so now in fits and starts. It's great. Just last week he and I were trying to crack one problem using regular expressions (yes, then we had two problems) and because there were two of us looking at the code it was solved!

Why is pair programming better?

Here's a few reasons why I think Pair Programming is very often better.

• Focus and Discipline - We set aside specific times and we sprint. We don't chat, we don't delete email, we code. And we also code with a specific goal or endpoint in mind.
• Collective ownership - I feel like we own the code together. I feel less ego about the code. Our hacks are our hacks, and our successes are shared.
• Personal growth - We mentor each other. We learn and we watch how the other moves around the code. I've learned new techniques, new hotkeys, and new algorithms.

Let's talk about the remote aspect of things. I'm remote. I also like to poke around on non-work-related tech on the side, as do many of us. Can I pair program remotely as well? Absolutely. I start with Skype, but I also use Google Hangouts, Join.me, TeamViewer, whatever works that day.

If you're a remote person on a larger team, consider remote pair programming. If you're an consultant  or perhaps you've left a big corporate job to strike off on your own, you might be lonely. Seriously, ask yourself that hard question. It's no fun to realize or have to declare you're a lonely coder, but I am and I will. I love my job and I love my team but if I go a day or two without seeing another human or spending some serious time on Skype I get really tense. Remote pair programming can really reduce that feeling of lonely coding.

I was at a small tech get together in Atlanta a few days ago and I knew that one person there was a singular coder at their small business while another at the table was an emerging college student with an emerging talent. I made a gentle suggestion that maybe they consider pairing up on some side projects and they both lit up.

Consider your networks. Are there people you've met at conferences or at local user groups or meetups that might be good remote pairing partners? This might be the missing link for you. It was for me!

Do you pair? Do you pair remotely? Let us all know in the comments.

* Stock photo purchased from ColorStock - Your customers are diverse, why aren't your stock photos?

Sponsor: Big thanks to Telerik for sponsoring the feed this week. Try Kendo UI by Progress: The most complete set of HTML5 UI widgets and JavaScript app tools helping you cut development time.

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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I've got an Xbox One that I love that is connected to a DirectTV HDTV Receiver that I love somewhat less. The setup is quite simple. Since I can control the DirectTV with the Xbox One and we like to switch between Netflix and Hulu and DirectTV we use the Xbox One to control everything.

The basic idea is this, which is quite typical with an Xbox One. In theory, it's amazing.

However, this doesn't always work. Often you'll turn on the whole system and the Xbox will say "Your TV Signal was lost. Make sure your cable or satellite box is on and plugged into the Xbox." This got so bad in our house that my non-technical spouse was ready to "buy a whole new TV." I was personally blaming the Xbox.

It turns out that's an issue of HDMI compliance. The DirectTV and other older cable boxes aren't super awesome about doing things the exact way HDMI like it, and the Xbox is rather picky about HDMI being totally legit. So how do I "clean" or "fix" my HDMI signal from my Cable/Satellite receiver?

I took at chance and asked on Reddit and this very helpful user (thanks!) suggested an HDMI splitter. I was surprised but I was ready to try anything so I ordered this 2 port HDMI powered splitter from Amazon for just US$20.

ADDING AN HDMI SPLITTED WORKS - TOTALLY SOLVED THE PROBLEM

It totally works. The Xbox One now does its "negotiations" with the compliant splitter, not with the Receiver directly and we haven't seen a single problem since.

If you have had this problem with your Xbox One then pick up a 2 port HDMI powered splitter and rejoice. This is a high quality splitter than doesn't change the audio signal and still works with HDCP if needed. Thanks internets!

Sponsor: Big thanks to Telerik for sponsoring the feed this week. Try Kendo UI by Progress: The most complete set of HTML5 UI widgets and JavaScript app tools helping you cut development time.

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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