.NET

C# Anonymous types

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Updated: 28 January 2023

Anonymous types provide a convenient way to encapsulate a set of read-only properties into a single object without having to explicitly define a type first.

var v = new { Amount = 108, Message = "Hello" };

C# Lambda expressions and anonymous functions

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Updated: 28 January 2023

A lambda expression is used to create an anonymous function. The lambda declaration operator => separates the lambda’s parameter list from its body.

Expression lambda. Returns the result of the expression

// (input-parameters) => expression

Statement lambda

// (input-parameters) => { <statement block> }

Action<string> greet = name =>
{
    string greeting = $"Hello {name}";
    Console.WriteLine(greeting);
};

// greet("World");

Input parameters

// none
Action line = () => Console.WriteLine();

// one
Func cube = x => x * x * x;
Func cube = (x) => x * x * x;

// two or more
Func testForEquality = (x, y) => x == y;

// with types
Func isTooLong = (int x, string s) => s.Length > x;

Discards specify input parameters which are not used in the expression

Func<int, int, int> constant = (_, _) => 42;

.NET development with Docker

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Updated: 06 March 2025

Establish a development environment inside a running container

# Try this
docker run -it \
--volume $(pwd):/source \
--workdir /source \
mcr.microsoft.com/dotnet/sdk:6.0

# or try this
docker run -it \
--volume $(pwd):/source \
--workdir /source \
mcr.microsoft.com/dotnet/sdk:7.0

# or this
docker run -it \
--volume $(pwd):/source \
--workdir /source \
mcr.microsoft.com/dotnet/sdk:8.0

# or this
docker run -it \
--volume $(pwd):/source \
--workdir /source \
mcr.microsoft.com/dotnet/sdk:9.0

# Jan 2025, image sdk:10.0 does not exist.

Create a hello world project

# from inside the container
dotnet new console --framework net7.0 --use-program-main --name myapp

Run the app

cd myapp
dotnet run

publish & start an application dll

https://github.com/dotnet/dotnet-docker/blob/main/samples/dotnetapp/Dockerfile

Dockerfile

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /source

# copy csproj and restore as distinct layers
COPY *.csproj .
RUN dotnet restore

# copy and publish app and libraries
COPY . .
RUN dotnet publish -c Release -o /app --self-contained false --no-restore

# final stage/image
FROM mcr.microsoft.com/dotnet/runtime:6.0
WORKDIR /app
COPY --from=build /app .
ENTRYPOINT ["dotnet", "source.dll"]

Build image based on Dockerfile above, in the same directory

docker build -t dndev .

Run a container

docker run dndev

.NET NuGet

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Updated: 30 June 2023

https://www.nuget.org/

Add a package

dotnet add package System.Data.OleDb --version 8.0.0-preview.5.23280.8

Remove package reference from a project file.

dotnet remove package System.Data.OleDb

Lists the package references for a project or solution.

dotnet list package

.NET

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Updated: 16 January 2025

.NET is an open source developer platform (i.e. the Languages & Libraries) for building different types of apps. The supported languages are C#, Visual Basic and F#.

Microsoft .NET and .NET Core Release History

Target platforms are:

  • .NET Core which runs on Windows, Linux and macOS.
  • .NET Framework for websites, services and apps on Windows only.
  • Xamarin / Mono, a .NET for mobile e.g. iOS devices, Apple Watch/TV Android.

https://docs.microsoft.com/dotnet
https://aka.ms/dotnethelloworld

The Host

A container which offers built-in services:

  • Dependency injection – a technique for achieving Inversion of Control between classes and their dependencies.
  • Configuration
  • Logging
  • Options pattern
  • Host Services

.NET 6 offers Generic DefaultHost which can be configured for the application use cases.

Hosted Service

A service which performs work in the background. Any reference type object which implements IHostedService is a background / hosted / worker service.

DI Service Container

Class dependencies can be registered in a service container.

.NET provides a built-in service container, IServiceProvider. Services are typically registered at the app’s start-up and appended to an IServiceCollection. Once all services are added BuildServiceProvider is used to create the service container.

Dependency Injection injects the service into the constructor of the class where it’s needed. The framework takes on the responsibility of creating an instance of the dependency and disposing of it when it’s no longer needed.

dotnet CLI

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Updated: 09 May 2025

sln

Add the PrimeService.Tests project to the current solution file

dotnet sln add ./PrimeService.Tests/PrimeService.Tests.csproj

add

Add a reference to lib.csproj inside app.csproj

dotnet add app/app.csproj reference lib/lib.csproj

Add or updates a package reference in a project file

dotnet add package docopt.net

new

Creates a new project, configuration file, or solution, based on the specified template. Templates which come pre-installed with the .NET SDK

Initiate a project for creating a command-line application

dotnet new console --name our_project

Initiate a project for creating a command-line application and generate an explicit Program class and Main method instead of top-level statements.

dotnet new console --name file-encrypt --use-program-main

Display a list of all installed templates

dotnet new list

Create a Class Library project

dotnet new classlib --name MyClassLib

run

Build and test the Release version of a console application

dotnet run --configuration Release

test

Run the tests in the project in the current directory

dotnet test

Runs tests whose fully qualified name contains theMethod

dotnet test --filter theMethod

clean

Clean up the output of the previous build. Both intermediate (obj) and final output (bin) folders are cleaned.

dotnet clean

restore

Restores the dependencies and tools for a project i.e. external libraries in NuGet packages. All dependencies become available in a local cache and can be used by the .NET CLI to build and run the application.

dotnet restore

dotnet

List installed Software Developer Kits

dotnet --list-sdks

List installed runtimes

dotnet --list-runtimes

build

Build a project and its dependencies using Release configuration

dotnet build --configuration Release

Build the project and its dependencies into a set of binaries.
The binaries include the project’s code in Intermediate Language (IL) files with a .dll extension.

dotnet build

publish

Publishes the application and its dependencies to a folder for deployment to a hosting system.

dotnet publish

Publish the app in Release configuration

dotnet publish --configuration Release

Attempt to target Linux

dotnet publish --runtime linux-x64 -p:PublishSingleFile=true --self-contained false

format

Formats code to match .editorconfig settings.

Verifies that no formatting changes would be performed. Terminates with a non zero exit code if any files would have been formatted

dotnet format --verify-no-changes

Only check the test directory

dotnet format --include=test/

workload

One or more optional workloads can be installed on top of the .NET SDK, to provide support for various application types, such as .NET MAUI and Blazor

dotnet workload install maui