AspNetCore.Mvc action filter for ensuring validation of both model state and all action parameters as a precondition to a MVC action

EnsureModelStateIsValid.cs

/// <summary>
///     This action filter ensures ModelState.IsValid is true as a precondition to entry into the MVC action
/// </summary>
/// <remarks>
///     This class also validates all action parameters unlike the default behavior of ModelState.IsValid
/// </remarks>
/// <see cref="https://blog.markvincze.com/how-to-validate-action-parameters-with-dataannotation-attributes/" />
public class EnsureModelStateIsValid : ActionFilterAttribute
{
    private static readonly ConcurrentDictionary<MethodInfo, ParameterInfo[]> MethodCache 
        = new ConcurrentDictionary<MethodInfo, ParameterInfo[]>();

    public override void OnActionExecuting(ActionExecutingContext context)
    {
        ValidateParameters(context);

        if (context.ModelState.IsValid) return;

        context.Result = new BadRequestObjectResult(context.ModelState);
    }

    private void ValidateParameters(ActionExecutingContext context)
    {
        var descriptor = context.ActionDescriptor as ControllerActionDescriptor;
        if (descriptor == null) return;

        foreach (var param in GetParameters(descriptor.MethodInfo))
        {
            object arg;
            context.ActionArguments.TryGetValue(param.Name, out arg);

            Validate(param, arg, context.ModelState);
        }
    }

    private void Validate(ParameterInfo parameter, object argument, ModelStateDictionary modelState)
    {
        var paramAttrs = parameter.CustomAttributes.Where(x => typeof(ValidationAttribute).IsAssignableFrom(x.AttributeType));

        foreach (var attr in paramAttrs)
        {
            var validationAttribute = parameter.GetCustomAttribute(attr.AttributeType) as ValidationAttribute;

            if (validationAttribute == null) continue;
            if (validationAttribute.IsValid(argument)) continue;

            modelState.AddModelError(parameter.Name, validationAttribute.FormatErrorMessage(parameter.Name));
        }
    }

    private static IEnumerable<ParameterInfo> GetParameters(MethodInfo method) => MethodCache.GetOrAdd(method, x => x.GetParameters());
}

@markvincze good catch that should be GetOrAdd(method, x => x.GetParameters())