Scott Hanselman

T4MVC and R4MVC - Roslyn code generators for ASP.NET Core tag helpers

September 7, '17 Comments [20] Posted in ASP.NET MVC | Open Source
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I've always loved the T4 text generator within Visual Studio. If you are looking for T4 within Visual Studio 2017 you need to install the "Visual Studio extension development" option within the installer to access it. However, T4 development seems stalled/done and if you want to utilize some of it.

There's a nice open source project called T4MVC that you can use with Visual Studio 2015 and ASP.NET MVC to create strongly typed helpers that eliminate the use of literal strings in many places. That means instead of:

@Html.ActionLink("Dinner Details", "Details", "Dinners", new { id = Model.DinnerID }, null)

T4MVC lets you write

@Html.ActionLink("Dinner Details", MVC.Dinners.Details(Model.DinnerID))

Fast forward to 2017 and that team is working on a new project called R4MVC...it's a code generator that's based on Roslyn, the .NET Compiler Platform (hence the R).

It also lets you update your @Html.ActionLinks to be strongly typed, but more importantly it lets you extend that to strongly typed taghelpers, so instead of:

<a asp-action="Details" asp-controller="Dinners" asp-route-id="@Model.DinnerID">Dinner Details</a>

you can write

<a mvc-action="MVC.Dinners.Details(Model.DinnerID)">Dinner Details</a>

It's generating the URL for that <a> tag using the method and parameter.

Using an ASP.NET Core 1.1 app (2.0 is coming soon they say) I'll add the NuGet packages R4Mvc.Tools and R4Mvc, making sure to "include prerelease."

Adding R4Mvc.Tools in NuGet

I'll run "Generate-R4MVC" in the Package Manager Console.

Generate-R4MVC

There is a new R4Mvc.generated.cs file that gets created, and inside it is a whole bunch of classes based on the files on disk. For example I can type @Links.css, or @Links.lib and start getting intellisense for all my files on disk like JavaScript or CSS.

Links.css

When returning a view, rather than return View("About") I can do return View(Views.About):

return View(Views.About)

The R4MVC project also has Tag Helpers so their mvc-action attribute gives you strong typing like this:

<a mvc-action="MVC.Home.Index()">

This R4MVC project is just getting started, but I'm sure they'd appreciate your support! Head over to https://github.com/T4MVC/R4MVC/issues and learn about what they are planning and perhaps help out!

What do you think? Do you think there's value in smarter or strongly-typed URL generation with ASP.NET?


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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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Cloud Database? NoSQL? Nah, just use CSVs and CsvHelper

September 2, '17 Comments [44] Posted in Open Source
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KISS - Keep it Simple, Stupid. While I don't like calling people stupid, I do like to Keep it Super Simple!

I was talking to Jeff Fritz on my team about a new system we're architecting. I suggested CosmosDB or perhaps Azure Table Storage. Then we considered the amount of data we were storing (less than 100 megs) and Jeff said...let's just use CSV files and CsvHelper.

First I was shocked. SHOCKED I SAY.

via GIPHY

Then I was offended

via GIPHY

But finally I was hey...that's a good idea.

via GIPHY

A fine idea in fact. Why use more moving parts than needed? Sure we could use XML or JSON, but for our project we decided rather than even bother with an admin site that we'd use Excel for administration! It edits CSV files nicely thank you very much.

Can you parse CSV files yourself? Sure, but it'll start getting complex as you move between data types, think about quotes, deal with headers, whitespace, encoding, dates, etc. CSV files can be MUCH more complex and subtle than you'd think. Really.

Here's what CsvHelper can do for you:

var csv = new CsvReader( textReader );
var records = csv.GetRecords<MyClass>();

Here you just get an array of some class - if your class's structure maps 1:1 with your CSV file. If not, you can map your class with a projection of the types in the CSV file.

public sealed class PersonMap : CsvClassMap<Person>
{
public PersonMap()
{
Map( m => m.Id );
Map( m => m.Name );
References<AddressMap>( m => m.Address );
}
}

public sealed class AddressMap : CsvClassMap<Address>
{
public AddressMap()
{
Map( m => m.Street );
Map( m => m.City );
Map( m => m.State );
Map( m => m.Zip );
}
}

And finally, just want to export a CSV from an Enumerable that mirrors what you want? Boom.

var csv = new CsvWriter( textWriter );
csv.WriteRecords( records );

Or do it manually if you like (hardcode some, pull from multiple sources, whatever):

var csv = new CsvWriter( textWriter );
foreach( var item in list )
{
csv.WriteField( "a" );
csv.WriteField( 2 );
csv.WriteField( true );
csv.NextRecord();
}

It won't replace SQL Server but it may just replace one-table SQLite's and "using a JSON file as a database" for some of your smaller projects. Check out CsvHelper's site and excellent docs here along with the CsvHelper GitHub here.


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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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Experimental: Reducing the size of .NET Core applications with Mono's Linker

August 29, '17 Comments [22] Posted in DotNetCore
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The .NET team has built a linker to reduce the size of .NET Core applications. It is built on top of the excellent and battle-tested mono linker. The Xamarin tools also use this linker so it makes sense to try it out and perhaps use it everywhere!

"In trivial cases, the linker can reduce the size of applications by 50%. The size wins may be more favorable or more moderate for larger applications. The linker removes code in your application and dependent libraries that are not reached by any code paths. It is effectively an application-specific dead code analysis." - Using the .NET IL Linker

I recently updated a 15 year old .NET 1.1 application to cross-platform .NET Core 2.0 so I thought I'd try this experimental linker on it and see the results.

The linker is a tool one can use to only ship the minimal possible IL code and metadata that a set of programs might require to run as opposed to the full libraries. It is used by the various Xamarin products to extract only the bits of code that are needed to run an application on Android, iOS and other platforms.

I'll add this line to a nuget.config in my project's folder. Note that NuGet will inherit global settings and ADD this line.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
<packageSources>
<add key="dotnet-core" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" />
</packageSources>
</configuration>

Then I'll add the IL Linker's NuGet package to my project with this command line command (or from Visual Studio):

dotnet add package ILLink.Tasks -v 0.1.4-preview-906439

The assemblies will automatically be "trimmed" when they are published (not built) so I'll build it twice, disabling it with a switch:

D:\github\TinyOS\OS Project>dotnet publish -c release -r win-x64 -o notlinked /p:LinkDuringPublish=false
Microsoft (R) Build Engine version 15.3 for .NET Core

TinyOSCore -> D:\github\TinyOS\OS Project\bin\Release\netcoreapp2.0\win-x64\TinyOSCore.dll
TinyOSCore -> D:\github\TinyOS\OS Project\notlinked\

D:\github\TinyOS\OS Project>dotnet publish -c release -r win-x64 -o linked
Microsoft (R) Build Engine version 15.3 for .NET Core

TinyOSCore -> D:\github\TinyOS\OS Project\bin\Release\netcoreapp2.0\win-x64\TinyOSCore.dll
TinyOSCore -> D:\github\TinyOS\OS Project\linked\

And here's the results:

image

You can also run it with  /p:ShowLinkerSizeComparison=true and get a nice table. I've trimmed the table as it's super long.

  TinyOSCore -> D:\github\TinyOS\OS Project\bin\Release\netcoreapp2.0\win-x64\TinyOSCore.dll
Before linking (B) After linking (B) Size decrease
----------- ----------- ----------- -----------
Total size of assemblies 48,025,824 16,740,056 65.14%
----------- ----------- ----------- -----------
TinyOSCore.dll 36,352 36,352 0.00%
Microsoft.Extensions.Configuration.dll 24,584 24,584 0.00%
Microsoft.Extensions.Configuration.Abstractions.dll 20,480 20,480 0.00%
Microsoft.Extensions.Configuration.Binder.dll 24,064 24,064 0.00%
Microsoft.Extensions.Configuration.FileExtensions.dll 22,528 22,528 0.00%
Microsoft.Extensions.Configuration.Json.dll 24,072 24,072 0.00%
Microsoft.Extensions.DependencyInjection.dll 46,600 46,600 0.00%
Microsoft.Extensions.DependencyInjection.Abstractions.dll 35,336 35,336 0.00%
Microsoft.Extensions.FileProviders.Abstractions.dll 17,920 17,920 0.00%
Microsoft.Extensions.FileProviders.Physical.dll 31,240 31,240 0.00%
Microsoft.Extensions.FileSystemGlobbing.dll 39,432 39,432 0.00%
Microsoft.Extensions.Options.dll 26,120 26,120 0.00%
Microsoft.Extensions.Options.ConfigurationExtensions.dll 16,904 16,904 0.00%
Microsoft.Extensions.Primitives.dll 33,800 33,800 0.00%
Newtonsoft.Json.dll 639,488 639,488 0.00%
Microsoft.CSharp.dll 1,092,096 392,192 64.09%
Microsoft.VisualBasic.dll 465,416 0 100.00%
Microsoft.Win32.Primitives.dll 18,968 4,608 75.71%
Microsoft.Win32.Registry.dll 85,008 0 100.00%
SOS.NETCore.dll 54,264 0 100.00%
System.AppContext.dll 14,336 2,560 82.14%
System.Buffers.dll 14,336 2,560 82.14%
System.Collections.Concurrent.dll 206,360 31,744 84.62%
System.Collections.Immutable.dll 2,378,264 0 100.00%
System.Collections.NonGeneric.dll 96,792 24,576 74.61%
System.Collections.Specialized.dll 88,608 15,360 82.67%
System.Collections.dll 326,664 52,224 84.01%

TinyOSCore -> D:\github\TinyOS\OS Project\bin\Release\netcoreapp2.0\win-x64\publish\

You can see in some places where there's no size decrease. That's because I'm using those assemblies completely. Some see a 100% decrease - they've been removed entirely - because I'm not using the Registry, for example. And some see a fractional decrease because I'm using some methods but not others.

You can check out the full instructions and try this yourself at https://github.com/dotnet/core/blob/master/samples/linker-instructions.md. Again, it's a work in progress.


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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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Referencing .NET Standard Assemblies from both .NET Core and .NET Framework

August 21, '17 Comments [39] Posted in DotNetCore | NuGet | Open Source
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Lots of .NET Projects sharing a .NET Standard LibraryI like getting great questions in email but I LOVE getting great questions in email with a complete and clear code repro (reproduction) that's in a git somewhere. Then I can just clone, build (many many bonus points for a clean build) and check out the bug.

I got a great .NET Core question and repro here https://github.com/ScarlettCode/Example. I forked it, fixed it, and submitted a PR. Here's the question and issue and today's fix.

The project has a C# library project (an assembly) that is written to the .NET Standard 2.0. You'll recall that the .NET Standard isn't a runtime or a library in itself, but rather an interface. They are saying that this library will work anywhere that the .NET Standard is supported, like Linux, Mac, and Windows.

Here's that main .NET Standard Library called "Example.Data" written in C#.

Then he had:

  • Windows Forms (WinForms) application in VB.NET using .NET "full" Framework 4.6
  • Console Application also using .NET Framework 4.6
  • Console Application using .NET Core 2.0

Each of these apps is referring to the Example.Data library. The Example.Data library then pulls in a database access library in the form of Microsoft.EntityFrameworkCore.InMemory via NuGet.

WinForms app -> Data Access library -> Some other library. A->B->C where B and C are packages from NuGet.

The .NET Core console builds and runs great. However, when the other projects are run you get this error:

Can't load
Could not load file or assembly
'Microsoft.EntityFrameworkCore, Version=2.0.0.0,
Culture=neutral, PublicKeyToken=adb9793829ddae60'
or one of its dependencies. The system cannot find
the file specified.

Pretty low level error, right? First thing is to check the bin folder (the results of the compile) for a project that doesn't run. Looks like there's no Microsoft.EntityFrameworkCore there. Why not? It's assembly "C" downstream of "A" and "B". EntityFramework's assembly is referred to by the Example.Data assembly...but why didn't it get copied in?

The "full" Framework projects are using the older .csproj format and by default, they use package.config to manage dependencies. The newer projects can reference Packages as first-class references. So we need to tell ALL projects in this solution to manage and restore their packages as "PackageReferences."

I can open up the .csproj file for the Framework projects and add this line within the first <PropertyGroup> like this to change the restore style:

 <RestoreProjectStyle>PackageReference</RestoreProjectStyle>

As Oren wisely says:

"Using .NET Standard requires you to use PackageReference to eliminate the pain of “lots of packages” as well as properly handle transitive dependencies. While you may be able to use .NET Standard without PackageReference, I wouldn’t recommend it."

I can also change the default within VS's Package Management options here in this dialog.

 <RestoreProjectStyle>PackageReference</RestoreProjectStyle> Default Package management format

Hope this helps.

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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Draft - .NET Glossary Diagram

August 17, '17 Comments [55] Posted in DotNetCore
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I'm working on this slide as support for this excellent .NET Glossary. It's not done yet, but I'm curious for your thoughts. Every system has terms and concepts that are initially unfamiliar but make sense once you grok them.

image

Here are these concepts used in an example sentence, for context:

  • Application Framework - “Are you using the ASP.NET Core web framework for that microservice?”
  • Metapackage - “I want to install the ASP.NET Core framework; it’s a package of packages”
  • Package/NuGet - “I know there’s a NuGet package for decoding JSON.”
  • Library/Assembly - “Now, you’ll compile your source into an assembly”
  • .NET Standard – “Which version of the .NET Standard specification does your assembly target?"
    • "My Apple Watch supports .NET Standard 1.6 but my Windows 10 laptop supports 2.0 with more APIs.”
  • C#, F#, VB, etc – “Which language did you use?”
  • .NET SDK - “Did you get the developer tools?”
  • CLR/CoreCLR – “Which runtime is your app using?”
  • An implementation of .NET is a runtime along with libraries that implement a version of the .NET Standard
    • “Are you using .NET Core, .NET Framework, or Mono for this project?”
  • Platform - An operating system and some hardware (ARM, x64, etc.)
    • “Is that an ASP.NET Core app running in Docker on a Raspberry Pi?”

Constructive feedback, please. This is a draft.


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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.