Saturday, 22 April 2017

How to create .NET Core Console application on Ubuntu


To create .NET project of desired type we can use .NET Core command line tool (dotnet). Let's see the list of all possible project types:

$ dotnet new

Template Instantiation Commands for .NET Core CLI.

Usage: dotnet new [arguments] [options]

Arguments:
template The template to instantiate.

Options:
-l|--list List templates containing the specified name.
-lang|--language Specifies the language of the template to create
-n|--name The name for the output being created. If no name is specified, the name of the current directory is used.
-o|--output Location to place the generated output.
-h|--help Displays help for this command.
-all|--show-all Shows all templates


Templates Short Name Language Tags
----------------------------------------------------------------------
Console Application console [C#], F# Common/Console
Class library classlib [C#], F# Common/Library
Unit Test Project mstest [C#], F# Test/MSTest
xUnit Test Project xunit [C#], F# Test/xUnit
ASP.NET Core Empty web [C#] Web/Empty
ASP.NET Core Web App mvc [C#], F# Web/MVC
ASP.NET Core Web API webapi [C#] Web/WebAPI
Solution File sln Solution

Examples:
dotnet new mvc --auth None --framework netcoreapp1.1
dotnet new classlib
dotnet new --help

To create Console application project we have to use console:
$ dotnet new console -o TestProject -n HelloWorld
Content generation time: 54.4945 ms
The template "Console Application" created successfully.

This creates a directory TestProject and in it project named HelloWorld and intial source code file:
$ ls
TestProject

$ cd TestProject/

/TestProject$ ls
HelloWorld.csproj Program.cs

HelloWorld.csproj:
/TestProject$ cat HelloWorld.csproj


Program.cs:
/TestProject$ cat Program.cs


Let's now update dependencies (NuGet packages) and tools specified in the project:
/TestProject$ dotnet restore
Restoring packages for /home/bojan/Downloads/test/TestProject/HelloWorld.csproj...
Generating MSBuild file /home/bojan/Downloads/test/TestProject/obj/HelloWorld.csproj.nuget.g.props.
Generating MSBuild file /home/bojan/Downloads/test/TestProject/obj/HelloWorld.csproj.nuget.g.targets.
Writing lock file to disk. Path: /home/bojan/Downloads/test/TestProject/obj/project.assets.json
Restore completed in 492.24 ms for /home/bojan/Downloads/test/TestProject/HelloWorld.csproj.

NuGet Config files used:
/home/bojan/.nuget/NuGet/NuGet.Config

Feeds used:
https://api.nuget.org/v3/index.json

This creates obj directory and various config files:
/TestProject$ ls
HelloWorld.csproj obj Program.cs

/TestProject$ cd obj/

/TestProject/obj$ ls
HelloWorld.csproj.nuget.g.props HelloWorld.csproj.nuget.g.targets project.assets.json

HelloWorld.csproj.nuget.g.props:
/TestProject/obj$ cat HelloWorld.csproj.nuget.g.props


HelloWorld.csproj.nuget.g.targets:
/TestProject/obj$ cat HelloWorld.csproj.nuget.g.targets


project.assets.json:
/TestProject/obj$ cat project.assets.json


We can now build the project and run the binary output:
/TestProject$ dotnet run
Hello World!

This command built the project and placed binary output and other build artifacts in newly created bin directory:
/TestProject$ ls
bin HelloWorld.csproj obj Program.cs

/TestProject$ cd bin

/TestProject/bin$ ls
Debug

/TestProject/bin$ cd Debug/

/TestProject/bin/Debug$ ls
netcoreapp1.1

/TestProject/bin/Debug$ cd netcoreapp1.1/

/TestProject/bin/Debug/netcoreapp1.1$ ls
HelloWorld.deps.json HelloWorld.dll HelloWorld.pdb HelloWorld.runtimeconfig.dev.json HelloWorld.runtimeconfig.json

.deps.json (dependencies JSON file) lists dependencies of the application:
/TestProject/bin/Debug/netcoreapp1.1$ cat HelloWorld.deps.json


.runtimeconfig.dev.json:
/TestProject/bin/Debug/netcoreapp1.1$ cat HelloWorld.runtimeconfig.dev.json


.runtimeconfig.json file specifies the shared runtime and its version for the application:
/TestProject/bin/Debug/netcoreapp1.1$cat HelloWorld.runtimeconfig.json


It might seem unexpected that the binary output is not .exe but .dll. This is because default .NET Core's deployment model is Framework-dependent deployment, where output assembly contains only compiled source and 3rd party dependencies but not .NET Core dependencies - assembly assumes that .NET Core Framework and runtime are installed on the target machine. This is why we have to use dotnet tool to run it:

/TestProject/bin/Debug/netcoreapp1.1$ dotnet HelloWorld.dll
Hello World!

The other type of deployment is Self-contained deployment in which case the output assembly is .exe and contains .NET Core dependencies and runtime - nothing else is necessary to be installed on the target system.


References:

.NET Core application deployment
.NET Core command-line interface (CLI) tools
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