Tag Archives: EFCore

Follow My Explorations into AWS for .NET Developers

Earlier this year, a friend who is a dev advocate for .NET on AWS reached out to me to see if I had any awareness at all about the support Amazon Web Services has for .NET developers and .NET applications. My answer was a definite no. I’m an Azure fan girl and had never even thought about .NET on AWS. When he started rattling off some of what’s available, APIs, tooling and a dedicated team, I was surprised.

And curious.

So I have spent quite a bit of time sating that curiosity. I’ve written two articles that were published in Code Magazine this summer and recently published a course on Pluralsight. I still love Azure (and all my friends who work on Azure), but I’m glad to have deeper familiarity of other options. This makes me a better developer as well as a better consultant to my clients.

My focus has not been on deep DevOps or comparisons to Azure. I just wanted to see how things work and try it out. And I was definitely impressed.

I did all of the work in Visual Studio on my Windows machine because there is a very feature rich extension called AWS Toolkit for Visual Studio. There are also extension for VS Code, JetBrains’ Rider and other IDEs (not just for .NET). The ones for VS Code and Rider are more focused on serverless apps so they don’t have all of the features of the one for Visual Studio.

Since I’ve already created so much content, I’m not going to reiterate it all here but I wanted to be sure you are aware of the articles and the course and…the fact that there is such a thing as .NET on AWS. Whether, like me, you are curious, or like others, you are a .NET developer who has been tasked to learn about using AWS, I hope you find them interesting. Here’s what I’ve created thus far:

Discovering AWS for .NET Developers
Article, May/June 2020 Code Magazine

This is about first foray. Creating an account, installing the toolkit into Visual Studio, creating a SQL Server database (on AWS), pointing a .NET Core 3.1 App with EF Core to use that database, then (using the AWS toolkit), publishing the application to AWS.

Transform Your ASP.NET Core API into AWS Lambda Functions
Article. July/August 2020 Code Magazine

This is the next foray. I took the application from the first article, transformed it into an AWS serverless application (mostly by adding a few files provided by a project template), then publishing it to AWS. In the end, AWS creates a Lambda serverless function in front of the API, which means you get the benefit of the billing that is only based on calls coming through function. That compares to the cost of having the application running and waiting for requests 24/7. 

Fundamentals of Building .NET Applications on AWS
Pluralsight course, 2.5 hours. Published Aug 7, 2020

The course leans on what I learned through the articles but also allowed me to spend more time explaining and teaching additional information. In the course, I walk through creating an account, installing the toolkit, creating the SQL Server database, publishing the .NET Core/EF Core app and publishing the serverless app. There is an additional lesson which is about publishing the application as docker containers, fully managed by AWS via a service called Fargate. There’s a lot more detail than the articles and I’m really walking you through  step by step from start to end for each task.

I hope you’ll find the articles and course helpful and interesting, especially, if like me, you had no idea all of this support for .NET devs exist from AWS. 

Pluralsight is totally free for the month of April

While many of you who read my blog are already Pluralsight subscribers with work or personal subscriptions, there are so many who do not have access. So Pluralsight is opening up the entire library of over 7,000 courses for people to watch while stuck at home. And you do not need to use a credit card to sign up.*

So whether you want to watch one my my courses such as 

Or any of the other 7,000+ courses from some of the most knowledgeable devs who happen to be great at teaching ….

Have at it!

There is also a free plan for business accounts.

Business Free April Details: “To support your team’s skill development during these new challenges, for a limited time we’ve extended our free team trial from 14 days to 30 days.”

*The fine print: Free April is open to anyone who is not a current, active subscriber. New free accounts and reactivated accounts opened through April 30, 2020 will have access to Pluralsight’s library of video courses through April. Payment information will not be required for new free accounts opened through April 30, 2020. New free accounts opened after May 1, 2020, will only have access to a portion of Pluralsight’s library and will require payment information.

Links to My Recent DDD+EFCore Content

Time to aggregate the various articles and videos I’ve created filled with lessons on how EF Core support for direct mapping of domain models to your relational databases has been improving:

Announcing: Deep Dive into EF Core 2-Day Workshop

Join me in London June 17-18 for a 2-day deep dive into Entity Framework Core.

This is a new addition to Skills Matter course catalog. Because it is a new course, we are looking to get feedback on the proposed list of topics to be covered. If you are interested in attending, your input will be helpful.

Is the list of topics too long for 2 days? Does it touch on what you would want to learn in an advanced class? You can provide feedback on the course description page.

Day 1: Leverage Advanced Features

  • High level review of EF Core differences from EF6
  • Implementing logging to capture EF Core’s database and in-memory activity. Learn about different types of logging data to be captured
  • Learn various approaches to seeding such as via database scripts, code or using the migration-based seeding introduced in EF Core 2.1. You’ll also learn when each approach may be appropriate
  • Using migrations during development,within source control and during deployments
  • Integration testing your EF Core code

Day 2: EF Core in Your Software Architecture

  • The Great Repository Debate: Pros and Cons of the Repository Pattern/Generic Repositories for exposing EF Core
  • Designing Data Layers/APIs
  • Understanding complicated mapping conventions and supplementing those with custom mappings using the Fluent API
  • Designing for performance
  • *Bonus topic* If all modules have been covered, you will also look at EF Core in Azure Functions and EF Core with Azure Cosmos DB (given adequate time)

Logging in EF Core 2.2 Has a Simpler Syntax–More like ASP.NET Core

Logging EF Core’s memory operations and SQL operations has evolved a few times since EF Core arrived. It takes advantage of the same underlying features that ASP.NET Core uses. If you are using ASP.NET Core, logging is baked in and it is really simple to turn it on for EF Core and add filtering. See Shawn Wildermuth’s blog post about EF Core logging in ASP.NET Core.

But if you aren’t using ASP.NET Core, it’s a little more complicated. Not terribly, but still there’s some extra work to do. It involves setting up an ILoggerFactory in your DbContext and defining any filters at the same time.

I wrote an article about this (with the focus being on taking advantage of the various available filters for EF Core logging) in MSDN Magazine earlier this …oh wait, it’s Jan 1, so I can say “last  year”.  Data Points – Logging SQL and Change-Tracking Events in EF Core. I also used it heavily in my EF Core 2 Getting Started course, EF Core 2:Mappings and EF Core 2.1: What’s New courses on Pluralsight. (Note that I’ve updated the sample code for the Getting Started course to EF Core 2.2 and put it on GitHub at github.com/julielerman/PluralsightEFCore2GettingStarted)

My article and courses were using Console apps to demonstrate EF Core behavior and therefore the ConsoleLoggerProvider to tie the logger to the console. Note that the Data Points article contains a lot of good details about the various types of filtering. So you can use the new syntax (below) to specify that there should be a filter, but be sure to read the article to learn about the flavors of filtering and what type of details you’ll be able to see based on the choices you make.

But the logging API has continued to evolve and is providing some of the same shortcuts that ASP.NET had created. And the ConsoleLoggerProvider has been deprecated. The API is not part of EF Core. It’s part of .NET Core. Both EF Core and ASP.NET Core use it.

If you are using EF Core 2.2, the syntax has changed (simplified) and it’s going to get even more streamlined in 3.0.

In fact, if you use the earlier syntax with 2.2, you’ll get a warning about the ConsoleLoggerProvider:

Obsolete(“This method is obsolete and will be removed in a future version. The recommended alternative is using LoggerFactory to configure filtering and ConsoleLoggerOptions to configure logging options.”)

For a point of comparison, here is an example of using theold syntax to turn on logging, only show logs related to database commands and only show messages that are tagged as “Information”.

EF Core 2.0 & 2.1 Logic

public static readonly LoggerFactory MyConsoleLoggerFactory
            = new LoggerFactory(new[] {
              new ConsoleLoggerProvider((category, level)
                => category == DbLoggerCategory.Database.Command.Name
               && level == LogLevel.Information, true) });

Once your logger factory field is defined in the context class you tell the DbContext to use it when configuring.

protected override void OnConfiguring
  (DbContextOptionsBuilder optionsBuilder)
  var connectionString = 

So it’s the creation of the logger factory whose syntax is a little convoluded. The newer API follows how ASP.NET Core lets you filter with an AddFilter method that takes the filters as parameters. No lambdas needed. Also configuring the filter is a separate bit of logic that tellig the logger that it should be tied to the console.

EF Core 2.2 Logic

With EF Core 2.2, you can set up the logger factory in the constructor or another method as long as it’s available when you are configuring the option builder. I’m creating it in a method then using that method as a parameter of UseLoggerFactory. I’m still filtering on showing only database commands and log details flagged as Information.

private ILoggerFactory GetLoggerFactory()
  IServiceCollection serviceCollection = new ServiceCollection();
  serviceCollection.AddLogging(builder =>
  return serviceCollection.BuildServiceProvider()

and then I’m calling GetLoggerFactory() in the UseLogging method on the optionsbuilder:


Packages and References

In order to use the AddConsole() method, you still have to use the Microsoft.Extensions.Logging.Console package that the earlier ConsoleLoggerProvider was in. However, you do not need a using statement for the namespace (as you did for the ConsoleLoggerProvider).

EF Core’s IsConfigured and Logging

I got a little confused about some behavior today and finally realized my mistake so thought I would share it. This mostly happens in demo apps that I’m building that are not using  ASP.NET Core.

In these cases, I typically stick the DbContext provider configuration in the OnModelConfiguring method. For example, if I’m using SQLite, then I would specify that in the method as such:

protected override void OnConfiguring
 (DbContextOptionsBuilder optionsBuilder)
   optionsBuilder.UseSqlite (@"Filename=Data/PubsTracker.db");

I also have been using the logging factory a lot. After defining it, I also configure it. I hadn’t thought much about where I was placig it so added it in randomly.

protected override void OnConfiguring 
  (DbContextOptionsBuilder optionsBuilder)
  optionsBuilder.UseLoggerFactory (MyConsoleLoggerFactory);
  optionsBuilder.UseSqlite (@"Filename=Data/PubsTracker.db");

Then I added in some tests to had to avoid the SQLite provider if the InMemory provider was already configured, so I wrapped the UseSqlite method with a check to see if the options builder was already configured.

protected override void OnConfiguring
  (DbContextOptionsBuilder optionsBuilder)
  optionsBuilder.UseLoggerFactory (MyConsoleLoggerFactory);
    optionsBuilder.UseSqlite (@"Filename=Data/PubsTracker.db");

But my logic wasn’t working. I was running some migrations but they were suddenly not recognizing the UseSqlite method. I’ve used this pattern so many times. It took me a while to realize what was going on. The UseLoggerFactory is a configuration!

I just had to move the UseLoggerFactory logic after the IsConfigured check and all was well.

This is one of those dumb things that seems so silly you wouldn’t imagine someone else would make such a mistake. But since it bit me, I thought it was worth sharing mostly for the sake of the next coder who is trying to solve the same problem.

New Pluralsight Course! EF Core 2: Getting Started

I’ve recently published my 19th course on Pluralsight.com: Entity Framework Core 2: Getting Started.

It’s 2hrs 40 minutes long and focuses on the basics.

This is using EF Core 2.0.1 in Visual Studio 2017.

Future plans: I’ve begun working on an intermediate level course to follow up and have others in the pipeline…such as a course to cover features of EF Core 2.1 when it gets released (I will wait until it has RTMd for stability) and other advanced topics. I am also planning to do a cross-platform version using VS Code on macOS because that’s my fave these days.

If you are not a Pluralsight subscriber, send me a note and I can give you a 30-day trial so you can watch the course. Be warned: the trial is akin to a gateway drug to becoming a subscriber.

Here is the table of contents for the course:

Introducing a New, Lighter Weight Version of EF   32m 40s
Introduction and Overview
What Is Entity Framework Core?
Where You Can Build and Run Apps with EF Core
How EF Core Works
The Path From EF6 to EF Core to EF Core
EF Core 2 New Features
Looking Ahead to EF Core 2.1 and Beyond
Review and Resources

Creating a Data Model and Database with EF Core    42m 36s
Introduction and Overview
Setting up the Solution
Adding EF Core with the NuGet Package Manager
Creating the Data Model with EF Core
Specifying the Data Provider and Connection String
Understanding EF Core Migrations
Adding Your First Migration
Inspecting Your First Migration
Using Migrations to Script or Directly Create the Database
Recreating the Model in .NET Core
Adding Many-to-many and One-to-one Relationships
Reverse Engineering an Existing Database
Review and Resources

Interacting with Your EF Core Data Model 34m 11s
Introduction and Overview
Getting EF Core to Output SQL Logs
Inserting Simple Objects
Batching Commands When Saving
Querying Simple Objects
Filtering Data in Queries
Updating Simple Objects
Disconnected Updates
Deleting Objects with EF Core
Review and Resources

Querying and Saving Related Data   20m 49s
Introduction and Overview
Inserting Related Data
Eager Loading Related Data
Projecting Related Data in Queries
Using Related Data to Filter Objects
Modifying Related Data
Review and Resources

Using EF Core in Your Applications    30m 52s
Introduction and Overview
EF Core on the Desktop or Device
The Desktop Application: Windows Presentation Foundation (WPF)
Creating the WPF Application
Walking Through the WPF Data Access
EF Core in ASP.NET Core MVC
Adding Related Data into the MVC App
Coding the MVC App’s Relationships
Review and Resources

The Secret to Running EF Core 2.0 Migrations from a NET Core or NET Standard Class Library

I have had two people that watched my Pluralsight EF Core Getting Started course (which will soon be joined by an EF Core 2: Getting Started course) ask the same question, which mystified me at first.

The were running migrations commands which caused the project to compile, but the commands did not do anything. For example, add-migration didn’t add a migration file. get-dbcontext did not return any information. The most curious part was there was no error message! I was able to duplicate the problem.

With EF6 it was possible to use migrations from a class library with no exe project in sight. EF Core migrations can run from a .NET Framework or .NET Core project but not .NET Standard. It needs a runtime. A common workaround is that even if you haven’t gotten to the UI part of your app yet, to just add a .NET Core console app project to the solution, add the EF Core Design Nuget package to it and set it as the startup project. But it’s still possible to do this without adding in a dummy project.

We already knew about the multi-targetting fix which solved an error when you try to run migrations from a .NET Standard library. But even with that fix in place, we were getting the mysterious nothingness.

The answer to the question was buried in a GitHub issue and in comments for the Migrations document in the EF Core docs. This same solution solved a problem I was having when trying to use migrations in a UWP app (again, not .NET Core or .NET Framework) that used a separate class library to host its DbContext.

I’m writing this blog post to surface the solution until it is resolved.

The solution that we used with EF Core 1.0 in order to run migrations from a .NET Standard library was to multi-target for .Net Standard (so you can use the library in a few places) and .NET Core (so you can run migrations).

That means replacing




Notice that the attribute name is now plural and there is a semi-colon between the two SDKs.

But there’s one more secret which is not in the documentation.

For .NET Standard 2.0 (and EF Core 2.0), you also need to add the following to csproj.


Now with the DbContext project set as the startup and ensuring that the package manager console (or command line) are pointing to the same project, your migration commands will work.

Thanks to Christopher Moffat who found the solution in the GitHub issues and shared it in the comments on the EF Core Package Manager Console Tools document.

Screenshot for Tony ..see my comment in reply to your comment below.

Domain-Driven Design Europe 2018 in Amsterdam

I’m excited to be attending and speaking at DDD Europe 2018 in Amsterdam on Feb 1-2 2018. It’s an honor to be on the speaker roster with so many DDD gurus and other people with amazing DDD experiences stories to share.

The lowest early-bird ticket prices can still be bought through Nov 30 at €599 (+21% VAT =  €724 (app. ~$860US +). The ticket will go to €699 (+VAT) from Dec 1-Dec31 and then to €749 (+VAT) until the conference.

Prior to the conference,  there are also 10 amazing workshops ranging from 1/2 day to 2 days across January 30 – 31st.

I’ll be doing a 2  hour workshop during the conference proper on using EF Core 2 to map DDD patterns in your domain. It will be a hands-on workshop and my intention is to build some koans for attendees to work with. Although the flavor of hands-on may shift as I continue to percolate ideas.

Watch my Domain-Driven Design Fundamentals course on Pluralsight