This is a forked version of the Result and Result<Ok> types from Functional Extensions for C# which swap in a list of Validation Errors for the single string error message found in the original, where each Validation Error consists of an optional list of field names and error message, similar to the System.ComponentModel.DataAnnotations set of functionality. And indeed, you can use Data Annotations and validate via the EnsureDataAnnotations() extension method.

The Result structs and extensions are a great foundation, but the single string Error inside Result and Result<Ok> were too limiting, while Result<Ok, Err> extensions were incomplete.

Adding all the extra functionality to Result<Ok, Err> just proved too cumbersome and was just to unwieldy in the end, so I instead chose to swap out the internals of Result Result<Ok> with an Error value I have found useful in the past, and which allows an easy way to plug in the System.ComponentModel.DataAnnotations style of declarative validation annotations. Initially I had intended to use a different naming convention than the original Result, but this project grew enough that it is a separate fork, and as such contains mirrors of the Maybe types from the original as well.

The ValidationError and Result classes are immutable, but the classes can be joined and chained together in a few different ways, as in using Combine() or Join().

• Propagate continueOnCapturedContext to new async methods (oops)
• More tests
• Documentation and examples
• Publish on nuget.org

A big thanks to the Functional Extensions for C# project contributors!

• Vladimir Khorikov
• Robert Sęk
• Sergey Solomentsev
• Malcolm J Harwood
• Dragan Stepanovic
• Ivan Novikov
• Denis Molokanov
• Gerald Wiltse
• yakimovim
• Alex Erygin
• Omar Aloraini