Using Enumerations in ASP.NET Core Routes

In gitclub-dotnet I wanted to use enumerations in routes. This can easily be done by implementing an IRouteConstraint. So let's do it!

All code can be found in a Git repository at:

https://github.com/bytefish/gitclub-dotnet

Implementing the EnumRouteConstraint

We start by implementing a IRouteConstraint, which will be used for matching incoming routes.

// Licensed under the MIT license. See LICENSE file in the project root for full license information.

namespace GitClub.Infrastructure.Mvc
{
    public class EnumRouteConstraint<TEnum> : IRouteConstraint
        where TEnum : struct
    {
        public bool Match(HttpContext? httpContext, IRouter? route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
        {
            var matchingValue = values[routeKey]?.ToString();

            return Enum.TryParse(matchingValue, true, out TEnum _);
        }
    }
}

We then need to configure the RouteOptions for ASP.NET MVC like this:

// Route Constraints
builder.Services.Configure<RouteOptions>(options =>
{
    options.ConstraintMap.Add("TeamRoleEnum", typeof(EnumRouteConstraint<TeamRoleEnum>));
    options.ConstraintMap.Add("OrganizationRoleEnum", typeof(EnumRouteConstraint<OrganizationRoleEnum>));
    options.ConstraintMap.Add("RepositoryRoleEnum", typeof(EnumRouteConstraint<RepositoryRoleEnum>));
});

Using the EnumRouteConstraint

And we can then use the Route Constraint like this:

// Licensed under the MIT license. See LICENSE file in the project root for full license information.

// ...

namespace GitClub.Controllers
{
    [Route("[controller]")]
    public class OrganizationsController : ControllerBase
    {
        // ...

        [HttpPut("{organizationId}/organization-roles/users/{userId}/{role:OrganizationRoleEnum}")]
        public async Task<IActionResult> AddUserOrganizationRole(
            [FromServices] OrganizationService organizationService,
            [FromServices] CurrentUser currentUser,
            [FromRoute(Name = "organizationId")] int organizationId,
            [FromRoute(Name = "userId")] int userId,
            [FromRoute(Name = "role")] OrganizationRoleEnum role,
            CancellationToken cancellationToken)
        {
            _logger.TraceMethodEntry();

            // ...        
        }

        // ...
    }
}

And that's it!