AutoMapper VS FluentValidation

AutoMapper

The 13.0 Upgrade Guide page was created back in April, but there is no sign of the release yet.

The most well-know is probably AutoMapper, but it's not universally liked.

AutoMapper - well for automapping

When working with AutoMapper, we often bump into runtime errors due to invalid mapping configuration, such as this one:

What problems will resolve automapper?

If you are a fan of data mappers, you might want to enhance the implementation with additional extension methods. Here is an example for AutoMapper.

I'm wondering myself. Most mappers like https://automapper.org/ will make a best effort mapper automatically via introspection. If this is just a DSL/annotation suite that requires explicit, complete mapping implementations then this strikes me as a re-implementation of parts of kotlin in kotlin.

Here is an example of Command handler with built-in Fluent Validation and fire and forget style:

There is an RFC called Problem Details (RFC7807) that standardizes how an error in an API should be responded to for the client. If you use Fluent validation, you may have noticed that the response is within this pattern.

here we're defining the input validation requirements using fluent validation rules. let's see what happens when the user input doesn't meet the above criteria. execute the same request in swagger with the following incorrect json content:

I remember FluentValidation being a nice library for this type of stuff.

Literally the code example in the front page: https://fluentvalidation.net/

https://www.nuget.org/packages/Newtonsoft.Json/ https://www.nuget.org/packages/AutoMapper/ https://www.nuget.org/packages/Dapper/ https://www.nuget.org/packages/FluentValidation/ https://www.nuget.org/packages/FluentAssertions/ https://www.nuget.org/packages/NUnit/ https://www.nuget.org/packages/xunit/ https://www.nuget.org/packages/YamlDotNet/ https://www.nuget.org/packages/Moq/ That is simply not true. Mature c# projects purposely maintain no downstream dependencies and is they do, it's to a major reputable lib. See for yourself - these are staple third party packages commonly used. Anything dependency starting with System or NETStandard is Microsoft maintained.

FluentValidator for validating and authorising certain fields.

Now that we know the importance of providing users with enough information about their requests and how it was processed, let’s focus on how we can configure our API to help us do that.One aspect of such meaningful experience is Request Validation (400 Error Range). For that purpose I am using a library called Fluent Validation.