dotnet add package Rollbar.Net.AspNet.Mvc

//...
using Rollbar;
using Rollbar.Net.AspNet;
//..

public class MvcApplication : System.Web.HttpApplication
{
  protected void Application_Start()
  {
    ConfigureRollbarInfrastructure();
    RollbarLocator.RollbarInstance.Info("Rollbar.NET is ready to roll!");


    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
  }

  protected void Application_Error()
  {
    var exception = Server.GetLastError();
    var httpContext = HttpContext.Current;
    IRollbarPackage packagingStrategy = 
      new ExceptionPackage(
      	exception, 
      	"EXCEPTION intercepted by MvcApplication.Application_Error()"
    );
    
    if (httpContext != null)
    {
      packagingStrategy = 
        new HttpContextPackageDecorator(packagingStrategy, httpContext);
    }
    
    RollbarLocator.RollbarInstance.Critical(packagingStrategy);
  }


  /// <summary>
  /// Configures the Rollbar infrastructure.
  /// </summary>
  private static void ConfigureRollbarInfrastructure()
  {
    // minimally required Rollbar configuration:
    RollbarInfrastructureConfig rollbarInfrastructureConfig = 
      new RollbarInfrastructureConfig(
        RollbarSamplesSettings.AccessToken, 
        RollbarSamplesSettings.Environment
    );
    // optionally, add data scrubbing options:
    RollbarDataSecurityOptions dataSecurityOptions = 
      new RollbarDataSecurityOptions();
    dataSecurityOptions.ScrubFields = new string[]
    {
      "access_token", // normally, you do not want scrub this specific field (it is operationally critical), but it just proves safety net built into the notifier... 
      "username",
    };
    rollbarInfrastructureConfig
      .RollbarLoggerConfig
      .RollbarDataSecurityOptions
      .Reconfigure(dataSecurityOptions);

    // initialize Rollbar infrastructure:
    RollbarInfrastructure.Instance.Init(rollbarInfrastructureConfig);

    // optionally, if you would like to monitor all Rollbar instances' internal events within your application:
    RollbarInfrastructure.Instance.QueueController.InternalEvent += 
      OnRollbarInternalEvent;

    // optionally, if you would like to monitor this Rollbar instance's internal events within your application:
    RollbarLocator.RollbarInstance.InternalEvent += 
      OnRollbarInternalEvent;

    // basic test:
    RollbarLocator
      .RollbarInstance
      .Info($"{typeof(MvcApplication).Namespace}: Rollbar is up and running!");
  }

  /// <summary>
  /// Called when rollbar internal event is detected.
  /// </summary>
  /// <param name="sender">The sender.</param>
  /// <param name="e">The <see cref="RollbarEventArgs"/> instance containing the event data.</param>
  private static void OnRollbarInternalEvent(object sender, RollbarEventArgs e)
  {
    Console.WriteLine(e.TraceAsString());

    RollbarApiErrorEventArgs apiErrorEvent = e as RollbarApiErrorEventArgs;
    if (apiErrorEvent != null)
    {
      //TODO: handle/report Rollbar API communication error event...
      return;
    }
    CommunicationEventArgs commEvent = e as CommunicationEventArgs;
    if (commEvent != null)
    {
      //TODO: handle/report Rollbar API communication event...
      return;
    }
    CommunicationErrorEventArgs commErrorEvent = e as CommunicationErrorEventArgs;
    if (commErrorEvent != null)
    {
      //TODO: handle/report basic communication error while attempting to reach Rollbar API service... 
      return;
    }
    InternalErrorEventArgs internalErrorEvent = e as InternalErrorEventArgs;
    if (internalErrorEvent != null)
    {
      //TODO: handle/report basic internal error while using the Rollbar Notifier... 
      return;
    }
  }

}

//...
using Rollbar.Net.AspNet.Mvc;
//...

public class FilterConfig
{
  public static void RegisterGlobalFilters(GlobalFilterCollection filters)
  {
    filters.Add(new HandleErrorAttribute());
    filters.Add(new RollbarExceptionFilter(
      "SOURCE: Sample.AspNet.MvcApp's RollbarExceptionFilter"
    ));
  }
}