README.md

Danom.Mvc

Danom.Mvc is a library that provides a set of utilities to help integrate the Danom library with common tasks in ASP.NET Core MVC applications.

Getting Started

Install the Danom.Mvc NuGet package:

PM>  Install-Package Danom.Mvc

Or using the dotnet CLI

dotnet add package Danom.Mvc

Controller

The DanomController class extends the base controller class to provide a set of methods to help work with Result, Option, and ResultOption types in ASP.NET Core MVC applications.

Option

The ViewOption method is used to render a view based on the presence of an Option value.

If the Option is Some, the view is rendered with the value. If the Option is None, the noneAction is invoked. By default, the noneAction returns a NotFound result.

A custom view name can be provided to render a view with a different name than the action.

Some examples demonstrating the use of ViewOption are shown below:

using Danom.Mvc;
using Microsoft.AspNetCore.Mvc;

public sealed class OptionController
    : DanomController
{
    public IActionResult OptionSome() =>
        ViewOption(
            option: Option.Some("Hello world"),
            viewName: "Detail");

    // Returns the ASP.NET default `NotFound` result
    public IActionResult OptionNone() =>
        ViewOption(
            option: Option<string>.NoneValue,
            viewName: "Detail");

    public IActionResult OptionNoneCustom() =>
        ViewOption(
            option: Option<string>.NoneValue,
            viewName: "Detail",
            noneAction: () => NotFound("Not found!"));
}

Result

The ViewResult method is used to render a view based on the presence of a Result value.

By default the ViewResult method will render the view with the value if the Result is Ok. If the Result is Error, the errorAction is invoked.

A custom view name can be provided to render a view with a different name than the action.

using Danom.Mvc;
using Microsoft.AspNetCore.Mvc;

public sealed class ResultController
    : DanomController
{
    public IActionResult ResultOk() =>
        ViewResult(
            result: Result<string, string>.Ok("Success!"),
            viewName: "Detail");

    public IActionResult ResultError() =>
        ViewResult(
            result: Result<string, string>.Error("An error occurred."),
            errorAction: errors => View("Detail", errors),
            viewName: "Detail");

}

Built into Danom is the ResultErrors type, which is particularly well suited for reporting model errors in ASP.NET Core MVC applications. The ViewResultErrors method, provided by the DanomController class, is a proxy for the View method that will inject the ResultErrors value into the model state.

When using ResultErrors as the error type, the ViewResultErrors will default the errorAction to inject the ResultErrors value into the model state.

using Danom.Mvc;
using Microsoft.AspNetCore.Mvc;

public sealed class ResultController
    : DanomController
{
    public IActionResult ResultOk() =>
        ViewResult(
            // notice the lack of second type parameter, which is inferred to be ResultErrors
            result: Result<string>.Ok("Success!"),
            viewName: "Detail");

    public IActionResult ResultError() =>
        ViewResult(
            result: Result<string>.Error("An error occurred."),
            viewName: "Detail");


    public IActionResult ResultErrorView() =>
        // can be used directly
        ViewResultErrors(
            errors: new("An error occurred."));
}

View

While not explicitly part of the Danom.Mvc library, there are some patterns that make rendering the Option type easier in Razor views. Two methods from the base library are especially valuable: TryGet and ToString.

The TryGet method is used to extract the value from an Option type. If the Option is Some, the value is assigned to the out parameter and the method returns true. If the Option is None, the method returns false.

The custom ToString method is used to convert the Option value to a string. If the Option is Some, the value is converted to a string. If the Option is None, the method returns the default value. The method optionally accepts a second parameter for the format string.

Consider the following type:

public record Person(
    string Name,
    Option<DateOnly> Birthdate,
    Option<string> Email);

The TryGet and ToString methods can be used in a Razor view to help render the optional properties.

@model Person

<h1>@Model.Name</h1>
<h2>Email: <i>@Model.Email.ToString("-")</i></h2>

@if (Model.Birthdate.TryGet(out var birthdate))
{
    var now = DateTime.Now;
    var a = (now.Year * 100 + now.Month) * 100 + now.Day;
    var b = (birthdate.Year * 100 + birthdate.Month) * 100 + birthdate.Day;
    var age = (a - b) / 10000;

    <p>You are born on @birthdate, and are @age years old.</p>
}
else
{
    <p>You are an ageless wonder!</p>
}

Find a bug?

There's an issue for that.

License

Built with ♥ by Pim Brouwers in Toronto, ON. Licensed under Apache License 2.0.