Precedence is given to configuration through the fluent API followed by data annotations and then conventions. Fluent API. While we mostly use fluent configuration for our code-first POCOs, we have found it useful to use data annotations for things like the table name, PKs, etc. I use both, wherever each is appropriate, in a project currently. Fluent offers features not exposed through DA. Let’s say we have started to build a web api to add new customers: Our NewCustomermodel is: We also have an action filter which will handle validation on the models and return a 400 if they are invalid: Startup.ConfigureServiceslooks like this to wire everything up: So, let’s say we want to make CustomerName a required field in the POST method on the newCustomermodel. I personally haven't ran into any issues with mixing the code first fluent api and data annotations. I have convention to put [Key] as an Annotation Attribute in Entity and rest of the configuration into FluentAPI (ForeignKeys mostly). How to send email to multiple recipients using python smtplib? Data Annotations is a simple attribute based configuration, which you can apply to your domain classes and its properties. There are two major ways by which we can override the convention. But, personally, when I run into some sort of issues around structuring my entities - first thing I do is to remove annotations if any - and move all to fluent. consistent and in one place. First, on your comments that you like to use the fluent API only. For more information see Data Annotations, Fluent API - Relationships, Fluent API - Types & Properties and Fluent API with VB.NET. Data Annotations work across multiple ORMs. The issue is that you are removing all conventions on load, then using Fluent API. But in my opinion you reach the limitations of DataAnnotations very quickly (except perhaps for extremely simple object models). since it makes it easier for non-EF components that don't have a reference to the ObjectContext to interact with these entities. Entity Framework Code First - Defining Foreign Keys using Data Annotations and Fluent API When using Entity Framework Code First approach, there are actually three ways to define foreign keys. And here’s why: It is easy to see which validation rule is related to which property because it is placed right above the property and it is quite self-explanatory You can freely mix use of annotations and Fluent API. For additional information regarding the use of Data Annotations and the Code First Fluent API refer to the MSDN Entity Framework documentation. You can define a configuration convention in the OnModelCreating() method and also in a custom class, similar to how you would define normal entity mappings with Fluent API. Is that true? I also wondered if there would be any crossover pain and I can honestly say I have yet to find any. 7 comments Labels. http://msdn.microsoft.com/en-us/data/jj591583.aspx, (Part 1) And I don't even know that. You can override the DbContext.OnModelCreating method and use a parameter modelBuilder of type ModelBuilder to configure domain classes. DbModelBuilder You can override the DbContext.OnModelCreating method and use a parameter modelBuilder of type DbModelBuilder to configure domain classes. 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Microsoft themselves have come out and said that Fluent Configuration for EF Core is an “Advanced” feature, but I feel like anything more than just dipping your toe into EF Core, you’re gonna run into a dead end with Data Annotations and have to mix in Fluent Configuration anyway. Composite keys can only be configured using the Fluent API - conventions will never setup a composite key and you can not use Data Annotations to configure one. Data Annotations only give us a subset of configuration options. things exactly as you'd want them. You can use Data Annotation attributes and Fluent API at the same time. Data Annotations permit you to explicitly mark a class property with one or more attributes, whereas the Code First Fluent API permits you to use code rather than attributes to achieve the same goal. Separate Configuration Classes. While MaxLength has a database counterpart, MinLength does not. It is a disadvantage of Data Annotations that, where complex validation is required, the model class can start to look somewhat cluttered; in contrast with Fluent Validation where the model stays nice and clean. Calls to the fluent API take precedence over any data annotations. Fluent API provides a full set of configuration options available in Code-First. They each have … Entity Framework gives precedence to Fluent API over Data Annotations attributes. And it ’ s implementation in ASP.NET Core API a standard data attributes. There any risk to doing this mixed configuration then conventions into any issues with Mixing the code First Fluent can! Acts as a Fluent API design pattern ( a.k.a Fluent Interface ) where the result is formulated by chaining... Mapping scenarios that can turn up the validation configuration, such as required or max validation. Can use data Annotation attributes and Fluent API to configure properties personally have n't ran into any with... 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