One of the places the Result
type really shines is input validation. It's a natural step in most workflows to validate input data before processing it, and the Result type is a great way to handle this. The Danom.Validation library provides a set of utilities to help with this, integrating with the wonderful FluentValidation library.
Install the Danom.Validation NuGet package:
PM> Install-Package Danom.Validation
Or using the dotnet CLI
dotnet add package Danom.Validation
The kitchen sink example below demonstrates the functionality delivered from this slim library built on top of Danom.
using Danom;
using Danom.Validation;
using FluentValidation;
public record Attendee(
string Name,
int Age,
Option<string> Email,
Option<string> AlternateEmail);
public class AttendeeValidator
: AbstractValidator<Attendee>
{
public AttendeeValidator()
{
RuleFor(x => x.Name).NotEmpty();
RuleFor(x => x.Age).GreaterThan(0);
RuleFor(x => x.Email).Required(x => x.EmailAddress());
RuleFor(x => x.AlternateEmail).Optional(x => x.EmailAddress());
}
}
var input =
new Attendee(
Name: "John Doe",
Age: 30,
Email: Option<string>.Some("[email protected]"),
AlternateEmail: Option<string>.None());
var result =
ValidationResult<Attendee>
.From<AttendeeValidator>(input);
result.Match(
x => Console.WriteLine("Input is valid: {0}", x),
e => Console.WriteLine("Input is invalid: {0}", e));