Yahoo Finance Api Console App

A simple Yahoo Finance api console application to learn various libraries. Contains simple functions to query stock prices and summaries.

Example Usage

In this example the historic price for Tesla is retrieved.

Behavior

• When run, the app immediately calls Startup.BuildService(). This behaves similarly to an Asp.Net Startup call by loading a configuration and then building a 'ServiceCollection' by adding services.

services.AddMediatR(typeof(Program));
services.AddAutoMapper(typeof(Program));
services.AddCommandLineParser(typeof(Program));
services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ValidationBehavior<,>));
services.AddValidatorsFromAssembly(typeof(Program).Assembly);

BuildRefitclient(configuration, services);
services.AddSingleton<CommandLineParser>();

• In Program the service collection is used to build an instance of CommandLineParser and args are passed to it.
• CommandLineParser parses the args, either printing an error/providing help or constructing an object.
• The object is passed to the IMediator instance and sent.
• If the object has a registered handler then it enters the mediator pipeline.
• Inside AbstractValidator validators matching the object type are applied, either throwing an error if validation fails or passing it to the handler.
• The corresponding handler constructs an api request and awaits a response.
• If the response is Ok then the response is mapped to a result type and returned.

Libraries used:

• Microsoft.Extensions.Configuration
  • Used to load appSettings.json containing the API base address, secrets and host.
• Microsoft.Extensions.DependencyInjection
  • Scans assembly for types and creates a service provider.
• CommandLineParser
  • Handles parsing input arguments into objects and providing a basic ux - help text, error messages etc.
• Refit
  • When configured automatically turns an interface into a REST Api client.
  • Used to create IStockApi.
• MediatR
  • Mediator pattern library, Mediator.Extensions.Microsoft.DependencyInjection automatically gets all valid handlers.
  • Receives request objects and sends them to a valid handler. Handlers send a HTTP request and map the response to a result.
  • Supports pipeline behavior to validate the requests before sending it.
• FluentValidation
  • By creating a custom IPipelineBehavior ValidationBehavior class we can requests validate being sent through MediatR.
  • Validation is performed using FluentValidation in custom classes inheriting from AbstractValidator.
  • Validators are scanned for when building services using FluentValidation.DependencyInjection, Validators are then injected into the custom ValidationBehavior class.
• AutoMapper
  • Scans the assembly for Profiles containing mapping rules.
  • IMapper takes objects and attempts to map into different types.