ASP.NET Core

IdentityServer4, ASP.NET Core API and a client with username/password

This is an end-to-end guide on how to quickly setup IdentityServer4, use it in your ASP.NET Core API for authentication, and finally login to your API from a client by asking a user for her/his username and password. It is divided in three parts that describe respectively the configuration of each one of the following three systems:

  • IdentityServer4
    Contains instructions on how to setup and configure a token service based on IdentityServer4, that follows the quick-start guides, keeping only the absolutely minimum requirements for this tutorial
  • ASP.NET Core API
    An API configured to use IdentityServer4 as a middleware that adds the spec compliant OpenID Connect and OAuth 2.0 endpoints
  • Client (API Consumer)
    For this post, just a Console Application that consumes a protected resource from the API

Make authenticated requests to IdentityServer4 protected resources, using the IdentityServer4.Contrib.HttpClientService nuget package. It’s open source on github, just follow these Getting Started instructions or take a look at at sample!

Read More »IdentityServer4, ASP.NET Core API and a client with username/password

Writing a custom OutputFormatter to return an Excel (.xlsx) from an action in ASP.NET Core API

As most of us, I already know my next week work schedule. It includes writing some actions in respond to a requirement for excel exports. It’s nothing new and its’s relatively easy with libraries like NPOI: you just create your excel on the fly and return a FileResult.

Read how to create an excel on the fly inside your action here: http://www.talkingdotnet.com/import-export-excel-asp-net-core-2-razor-pages/

And that could be the end of story for that requirement, but while walking home for the weekend I remembered about the XmlSerializerOutputFormatter I read on Microsoft Docs. The idea was to write my own ExcelOutputFormatter to respond to client requests with an Excel instead of a JSON.

Read More »Writing a custom OutputFormatter to return an Excel (.xlsx) from an action in ASP.NET Core API

Publishing ASP.NET Core: An error occurred while starting the application

Have you seen this error?
An error occurred while starting the application.
.NET Core <version> | Microsoft.AspNetCore.Hosting <version> | Microsoft Windows <version> | Need help?

It looks like this in your browser:

Besides that one hint, that the error is while starting, it’s not very descriptive, right?

Althouth there many things that could go wrong and the proper way is to actually troubleshoot the error, I end up googling about this for over an hour! In my search I found numerous articles but it turned out that for me the solution was simple!
Read More »Publishing ASP.NET Core: An error occurred while starting the application

Parameterized Raw SQL Queries with Entity Framework: How to Unit Test with SQLite

Entity Framework Core allows you to drop down to raw SQL queries when working with a relational database. This can be
useful, because raw SQL queries can return entity types or, starting with EF Core 2.1, query types that are part of
your model, but it could also be a problem when it comes down to Unit Testing.

Read More »Parameterized Raw SQL Queries with Entity Framework: How to Unit Test with SQLite