.net – “.NET Core”

.net corenet

Recently in an official .NET Framework Blog it was announced that .NET Core is going open source.

Ironically, the author mentions that what .NET Core is will be explained in the next post. Some more details are mentioned in another announcement post.

From a supplied diagram:

.NET Core diagram

and articles text itself, I would assume that .NET Core (beside obvious things like being open-sourced) is a modular re-implementation of the full .NET. I.e. framework components are loaded as necessary, much like NuGet packages are loaded now. And now ASP.NET 5 is one of the modules that is already implemented. Is my understanding of .NET Core correct? Maybe I'm missing something?

I have found a recent article which I found both short and very good. It covers .NET Standard, .NET Core, and .NET Framework and their relationship. I highly recommend it.

Best Answer

From the .NET blog Announcing .NET 2015 Preview: A New Era for .NET:

.NET Core has two major components. It includes a small runtime that is built from the same codebase as the .NET Framework CLR. The .NET Core runtime includes the same GC and JIT (RyuJIT), but doesn’t include features like Application Domains or Code Access Security. The runtime is delivered via NuGet, as part of the [ASP.NET Core] package.

.NET Core also includes the base class libraries. These libraries are largely the same code as the .NET Framework class libraries, but have been factored (removal of dependencies) to enable us to ship a smaller set of libraries. These libraries are shipped as System.* NuGet packages on NuGet.org.

And:

[ASP.NET Core] is the first workload that has adopted .NET Core. [ASP.NET Core] runs on both the .NET Framework and .NET Core. A key value of [ASP.NET Core] is that it can run on multiple versions of [.NET Core] on the same machine. Website A and website B can run on two different versions of .NET Core on the same machine, or they can use the same version.

In short: first, there was the Microsoft .NET Framework, which consists of a runtime that executes application and library code, and a nearly fully documented standard class library.

The runtime is the Common Language Runtime, which implements the Common Language Infrastructure, works with The JIT compiler to run the CIL (formerly MSIL) bytecode.

Microsoft's specification and implementation of .NET were, given its history and purpose, very Windows- and IIS-centered and "fat". There are variations with fewer libraries, namespaces and types, but few of them were useful for web or desktop development or are troublesome to port from a legal standpoint.

So in order to provide a non-Microsoft version of .NET, which could run on non-Windows machines, an alternative had to be developed. Not only the runtime has to be ported for that, but also the entire Framework Class Library to become well-adopted. On top of that, to be fully independent from Microsoft, a compiler for the most commonly used languages will be required.

Mono is one of few, if not the only alternative implementation of the runtime, which runs on various OSes besides Windows, almost all namespaces from the Framework Class Library as of .NET 4.5 and a VB and C# compiler.

Enter .NET Core: an open-source implementation of the runtime, and a minimal base class library. All additional functionality is delivered through NuGet packages, deploying the specific runtime, framework libraries and third-party packages with the application itself.

ASP.NET Core is a new version of MVC and WebAPI, bundled together with a thin HTTP server abstraction, that runs on the .NET Core runtime - but also on the .NET Framework.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – the difference between const and readonly in C#

Apart from the apparent difference of

having to declare the value at the time of a definition for a const VS readonly values can be computed dynamically but need to be assigned before the constructor exits.. after that it is frozen.
const's are implicitly static. You use a ClassName.ConstantName notation to access them.

There is a subtle difference. Consider a class defined in AssemblyA.

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly int I_RO_VALUE;
  public Const_V_Readonly()
  {
     I_RO_VALUE = 3;
  }
}

AssemblyB references AssemblyA and uses these values in code. When this is compiled:

in the case of the const value, it is like a find-replace. The value 2 is 'baked into' the AssemblyB's IL. This means that if tomorrow I update I_CONST_VALUE to 20, AssemblyB would still have 2 till I recompile it.
in the case of the readonly value, it is like a ref to a memory location. The value is not baked into AssemblyB's IL. This means that if the memory location is updated, AssemblyB gets the new value without recompilation. So if I_RO_VALUE is updated to 30, you only need to build AssemblyA and all clients do not need to be recompiled.

So if you are confident that the value of the constant won't change, use a const.

public const int CM_IN_A_METER = 100;

But if you have a constant that may change (e.g. w.r.t. precision).. or when in doubt, use a readonly.

public readonly float PI = 3.14;

Update: Aku needs to get a mention because he pointed this out first. Also I need to plug where I learned this: Effective C# - Bill Wagner

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C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – the difference between const and readonly in C#

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