DDD Value Objects With Entity Framework Core

For those who aren’t familiar, there is a concept in Domain Driven Design that distinguishes between objects with identity (entities) and those without (value objects). When we model the domain we typically think in terms of entities which are then persisted and modified over time. They form the basis for which we describe the business and interact with it, and often times, entities are the only objects developers create when modeling the system. Value objects provide a wealth of benefits though when applied appropriately.

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Why You Should Read the .NET Core Source Code

In the first five years that I was working as a developer I didn’t once bother to read the .NET framework source code. I’m going to go out on a limb and say that this is probably the case for most software developers. We work with the .NET framework and associated tools and libraries every day, but we seldom care about how they really work or what’s contained within. Now, don’t get me wrong, the whole point of a framework is to shield you from having to know the underlying implementation details and knowing the entire framework is not necessary. I would argue though that knowing parts of the framework and how they work opens up opportunities and affords certain benefits.
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Paging in Entity Framework Core

If you’re using Entity Framework Core and building any non-trivial enterprise application then using data tables with paging is almost a certainty. There are two ways to do this: server side and client side. Which one you choose depends on your design and your needs. There are pros and cons associated with both so you need to choose the correct approach for what you want to accomplish. Continue reading “Paging in Entity Framework Core”

Query Filters and Automated Audit Columns

I wanted to write a quick post about using query filters and automatically populating audit columns in Entity Framework Core since I see a lot of people doing this manually still. A common scenario in most applications is to do soft deletes on everything, typically with a column like “IsDeleted”. Another common scenario that is found almost universally in every system are audit columns like “DateCreated” and “DateUpdated”. This is actually very simple to implement, so this is going to be a fairly short post.
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Maximizing Entity Framework Core Query Performance

Entity Framework Core query performance is something that comes up often when working on projects that rely on it heavily. I have often heard that Entity Framework is not performant enough which then leads to everything being written as a stored procedure. Usually this happens for two main reasons: developers aren’t familiar with how to write queries in a performant manner and developers that are more comfortable with SQL want to develop everything in their technology of choice. Entity Framework is not a silver bullet for everything. There are times when it simply can’t deliver the performance needed or when it is simply functionally incapable of doing what is necessary due to limitations of the framework. That being said, there is no reason you can’t write the vast majority of your application with it and reap all the benefits it provides.
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ASP.NET Core Request Post Processing

If you’ve worked with Asp.Net Core to create APIs then you have more than likely run into situations where you needed to return different sets of data for the same model. One way to accomplish this is request post processing using an ActionFilter. Lets start with a common scenario. We have an internal enterprise application and we have different types of users in the system. Users can call our API to get data on other users depending on their permission levels. We have three different types of users: Admin, HelpDesk, and Employee. Our class looks like this:
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Dealing with Validation – Domain vs Contextual

I’ve always found validation to be one of the most difficult and tedious aspects of writing enterprise software. No matter how you organize your rules, you are going to usually end up with duplication. To make matters worse, the rules aren’t written by developers, they are created by the business. This causes a disconnect between knowledge and domain experts, and the people who are implementing the validation in the code. As the rules change over time, and as the developers who originally worked on the system move on, the validation becomes increasingly difficult to manage. As the system matures, it ultimately ends up becoming a significant source of pain for all those involved. That’s assuming, of course, that you even have validation in the first place.
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