.Net Core Override Controller Route for Generic Controller

Question

I'm writing a RestFramework and I'm trying to figure out how I can allow the users to create a custom name for a generic controller. I'm registering my generic controllers like so:

public class GenericControllerFeatureProvider : IApplicationFeatureProvider<ControllerFeature>
{
    public void PopulateFeature(IEnumerable<ApplicationPart> parts, ControllerFeature feature)
    {
        foreach (var entityConfig in _entityConfigurations)
        {
            var entityType = entityConfig.Type;
            var typeName = entityType.Name + "Controller";
            if (!feature.Controllers.Any(t => t.Name == typeName))
            {
                var controllerType = typeof(GenericController<>)
                    .MakeGenericType(entityType.AsType())
                    .GetTypeInfo();

               //Normally I would expect there to be an overload to configure the controller name
               //feature.Controllers.Add(controllerType, entityConfig.ControllerName);
            }
        }
    }
}

How ever I need to figure out a way that I can override the route for the controllers. The only information about this in the documentation shows how to create a controller convention like so:

public class GenericControllerNameConvention : Attribute, IControllerModelConvention
{
    public void Apply(ControllerModel controller)
    {
        if (controller.ControllerType.GetGenericTypeDefinition() != 
        typeof(GenericController<>))
        {
            return;
        }

        var entityType = controller.ControllerType.GenericTypeArguments[0];
        controller.ControllerName = entityType.Name;
    }
}

This will not work since it is done at compile time. I need user to be able to override the controller name on Startup, How can I Achieve this?

Answer 1

Based on your comment and code you were pretty much on par with how you would achieve this. Note I have cut down the example quite a bit so I could setup a test.

Say I have a basic generic controller as:

public class GenericController<T> : Controller
    where T: class
{

    public IActionResult Get()
    {
        return Content(typeof(T).FullName);
    }
}

I now have a typed controller with Get action. Now most of your code was right on the money. So my Feature Provider as (note i have a static array of types):

public class GenericControllerFeatureProvider : IApplicationFeatureProvider<ControllerFeature>
{
    public void PopulateFeature(IEnumerable<ApplicationPart> parts, ControllerFeature feature)
    {
        foreach (var entityConfig in ControllerEntity.EntityTypes)
        {
            var entityType = entityConfig;
            var typeName = entityType.Name + "Controller";
            if (!feature.Controllers.Any(t => t.Name == typeName))
            {
                var controllerType = typeof(GenericController<>)
                    .MakeGenericType(entityType)
                    .GetTypeInfo();

                feature.Controllers.Add(controllerType);
            }
        }
    }
}

Next the IControllerModelConvention implementation.

public class GenericControllerModelConvention : IControllerModelConvention
{
    public void Apply(ControllerModel controller)
    {
        if (!controller.ControllerType.IsGenericType || controller.ControllerType.GetGenericTypeDefinition() != typeof(GenericController<>))
        {
            return;
        }

        var entityType = controller.ControllerType.GenericTypeArguments[0];
        controller.ControllerName = entityType.Name + "Controller";
        controller.RouteValues["Controller"] = entityType.Name;
    }
}

And finally the startup is where all the magic happens. Basically we register the IControllerModelConvention into the MVC convention options, and then register the FeatureProvider.

public void ConfigureServices(IServiceCollection services)
{
    var mvcBuilder = services.AddMvc();
    mvcBuilder.AddMvcOptions(o => o.Conventions.Add(new GenericControllerModelConvention()));
    mvcBuilder.ConfigureApplicationPartManager(c =>
    {
        c.FeatureProviders.Add(new GenericControllerFeatureProvider());
    });
}

From my review two things struck me.

1. I am not sure why you have your GenericControllerNameConvention as an attribute?
2. You should implicitly set the Controller Route Value to your entity type (not the type + name).

Given two entities (EntityA and EntityB) the result of the controllers is

/Entitya/get/ prints WebApplication11.Infrastructure.EntityA

/Entityb/get/ prints WebApplication11.Infrastructure.EntityB