public interface IAction
{
    GatewayResponseHandlerResult Run();
}

public abstract class GatewayResponseHandler
{
    protected GatewayResponseHandlerResult Result = new GatewayResponseHandlerResult();

    private GatewayResponseHandlerResult Handle(GatewayResponse Response)
    {
        //specific handling code omitted
    }
}

public class GatewayResponseHandlerResult
{
    public bool Succeeded;
    public bool Failed;
    public bool Errored;
    public object Result { get; set; }

    public void SetAsSuccess()
    {
        Succeeded = true;
        Failed = false;
        Errored = false;
    }

    public void SetAsFailure()
    {
        Succeeded = false;
        Failed = true;
        Errored = false;
    }

    public void SetAsError()
    {
        Succeeded = false;
        Failed = false;
        Errored = true;
    }
}

public sealed class LoginAction : IAction
{
    private string Username;
    private string Password;

    public LoginAction(string Username, string Password)
    {
        this.Username = Username;
        this.Password = Password;
    }

    public GatewayResponseHandlerResult Run()
    {
        try
        {
            GatewayResponse LoginResponse = GatewayRequest.Login(Username, Password);
            return GatewayResponseHandler.Handle(LoginResponse);
        }
        catch (Exception ex)
        {
            throw ex.Log();
        }
    }
}

sealed class LoginHandler : GatewayResponseHandler
{
    protected override bool CanHandle()
    {
        return Response.action == GatewayAction.LOGIN;
    }

    protected override GatewayResponseHandlerResult ProcessError(Exception ex = null)
    {
        Result.SetAsError();
        return Result;
    }

    protected override GatewayResponseHandlerResult ProcessFailure()
    {
        Result.SetAsFailure();
        return Result;
    }

    protected override GatewayResponseHandlerResult ProcessSuccess()
    {
        try
        {
            if (Response.result_code == (int)ResponseCodes.SuccessCode.MFA_REQUIRED)
            {
                //specific MFA handling omitted
            }
            else if (Response.result_code == (int)ResponseCodes.SuccessCode.PW_RESET_REQUIRED)
            {
                //specific password reset code omitted
            }

            MessageBox.Show("Login successful");
            Result.SetAsSuccess();
        }
        catch (Exception Ex)
        {
            ProcessError(Ex);
            Result.SetAsError();
        }
        return Result;
    }
}

public interface IActionArgs{}

public class LoginActionArgs : IActionArgs
{
    public string Username;
    public string Password;
}

public abstract class Action
{
    public static GatewayResponseHandlerResult Run(IActionArgs ActionArgs)
    {
        throw new NotImplementedException();
    }
}

public sealed class LoginAction : IAction
{
    public static new GatewayResponseHandlerResult Run(IActionArgs ActionArgs)
    {
        //code omitted
    }
}