.NET Core 上手体验 Hello World

别人开源是种奉献精神, 微软突然把 .Net Framework 也开源, 人们看到的却是一种野心, 现在 .NET Core 开源还真正跨平台了, 真是雄心壮志啊.

本人 Java 多年, 但不可否认 C# 是一个很好的语言, 我认为单纯从语言上来说要优于 Java 语言, 所以 .NET Core 搭上 C# 力量更是不能小觑, 不得不摸索一下.

之前虽有浅尝 .NET Core 的 Hello World,   以及最简单的 ASP.NET 应用, 但未有成文, 在此再作演练一番以备忘.

安装 .NET Core

本人所用平台为 Mac, 所以当打开 .NET Core 的首页面 https://www.microsoft.com/net/core 时直接激活了 Mac 标签, 在这个页面我们知道 .NET Core 支持 Windows, Linux, Mac; 还有现成的 Docker 镜像拉下即用. .NET Core 当前版本是 1.0, 可以照着官方向导来做, 不过我倾向于全控制台来完成. 首先你的 Mac 得先有个 brew,  现在用 port 管理应用比较少了吧.

说白了, 安装 .NET Core 只需要用 brew cask install dotnet, 第一条命令没事都应该运行一下的, 发现有可升级的就运行一下 brew upgrade.

brew cask install dotnet 会检测是否有 openssl, 没有的话自动安装, 接着帮你下载 dotnet 安装包装上:

➜ brew cask install dotnet
==> Caveats
The latest version of OpenSSL is required to use .NET Core.
It was already installed, but you may need to link it:
ln -s /usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib /usr/local/lib/
ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/
Zsh users may need to symlink the dotnet binary:
ln -s /usr/local/share/dotnet/dotnet /usr/local/bin
==> Satisfying dependencies
==> Installing Formula dependencies from Homebrew
openssl ... done
complete
==> Downloading https://download.microsoft.com/download/0/A/3/0A372822-205D-4A86-BFA7-084D2CBE9EDF/dotnet-dev-osx-x64.1.0.0-preview2-003121.
Already downloaded: /Users/Yanbin/Library/Caches/Homebrew/Cask/dotnet--1.0.0-preview2-003121.pkg
==> Verifying checksum for Cask dotnet
==> Running installer for dotnet; your password may be necessary.
==> Package installers may write to any location; options such as --appdir are ignored.
Password:
==> installer: Package name is Microsoft .NET Core 1.0.0 - SDK Preview 2 (x64)
==> installer: Upgrading at base path /
==> installer: The upgrade was successful.
? dotnet was successfully installed!

为什么是 brew cask install dotnet 而不是 brew install dotnet 呢? 没问题, 可以试一下

➜ brew install dotnet
Error: No available formula with the name "dotnet"
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching taps...
This formula was found in a tap:
Caskroom/cask/dotnet
To install it, run:
brew install Caskroom/cask/dotnet

brew install Caskroom/cask/dotnet 和  brew cask install dotnet 是一样的. 这里没有遵照官方文档去手工下载那个安装文件 dotnet-dev-osx-x64.1.0.0-preview2-003121.pkg 来执行, 我们做的更自动化.

装好了 openssl 和 .NET Core 之后按照提示运行下

如果不执行上面头两条命令, 我们在后面执行  dotne 命令时就会看到类似于这样的错误

Unhandled Exception: System.TypeInitializationException: The type initializer for 'Crypto' threw an exception. ---> System.TypeInitializationException: The type initializer for 'CryptoInitializer' threw an exception. ---> System.DllNotFoundException: Unable to load DLL 'System.Security.Cryptography.Native': The specified module could not be found.
(Exception from HRESULT: 0x8007007E)
at Interop.CryptoInitializer.EnsureOpenSslInitialized()
at Interop.CryptoInitializer..cctor()
...................................................

现在就可以执行 dotnet 命令了, 它是你与 .NET Core 交互的门户, 也是一个构建工具.

创建 Hello World 项目

安装过程到此结束, 马上过渡到一个最简单的 Hello World 控制台程序的练习了

第一次执行  dotnet new 命令时间长一点点, 可能一分钟, 以后就快了. 执行完了提示 Created new C# project in /Users/Yanbin/Desktop/hwapp, 并且创建了两个文件

1. Program.cs  这是一个标准的 Hello World 程序
   
   namespace HelloWorld { class Hello { static void Main(string[] args) { System.Console.WriteLine("Hello World!"); } } }

   1 2 3 4 5 6 7 8 9

   namespace HelloWorld {     class Hello {                 static void Main(string[] args)         {             System.Console.WriteLine("Hello World!");         }     } }

2. project.json  这是一个项目配置文件, 内容如下

运行 Hello World 程序

➜ hwapp$ dotnet restore
log : Restoring packages for /Users/Yanbin/Desktop/hwapp/project.json...
log : Writing lock file to disk. Path: /Users/Yanbin/Desktop/hwapp/project.lock.json
log : /Users/Yanbin/Desktop/hwapp/project.json
log : Restore completed in 1273ms.
hwapp$ dotnet run
Project hwapp (.NETCoreApp,Version=v1.0) will be compiled because expected outputs are missing
Compiling hwapp for .NETCoreApp,Version=v1.0
Compilation succeeded.
0 Warning(s)
0 Error(s)
Time elapsed 00:00:05.7311046

Hello World!

dotnet restore 会生成一个 project.lock.json 文件, 它是 dotnet run 必须的. 它像是 Visual Studio 中的 Solution 文件.

实质运行的就是那个  bin/Debug/netcoreapp1.0/hwapp.dll 文件, 比如我们可以执行

➜ hwapp$ dotnet bin/Debug/netcoreapp1.0/hwapp.dll
Hello World!

dotnet run 之后生成的文件如下

➜ hwapp$ tree
.
├── Program.cs
├── bin
│   └── Debug
│   └── netcoreapp1.0
│   ├── hwapp.deps.json
│   ├── hwapp.dll
│   ├── hwapp.pdb
│   ├── hwapp.runtimeconfig.dev.json
│   └── hwapp.runtimeconfig.json
├── obj
│   └── Debug
│   └── netcoreapp1.0
│   ├── dotnet-compile-csc.rsp
│   ├── dotnet-compile.assemblyinfo.cs
│   └── dotnet-compile.rsp
├── project.json
└── project.lock.json

dotnet 其他命令

dotnet 的其他几个命令如下, 用 dotnet --help 查看

new Initialize a basic .NET project
restore Restore dependencies specified in the .NET project
build Builds a .NET project
publish Publishes a .NET project for deployment (including the runtime)
run Compiles and immediately executes a .NET project
test Runs unit tests using the test runner specified in the project
pack Creates a NuGet package

现在对 .NET Core 有了一个基本的感观认识了, 接下来看看如何用 ASP.NET Core, 用 .NET Core 做网站了.

附录: .NET Core Tutorials