Type or NameSpace "BlobAttribute" Not Found

I am following along a Pluralsight Tutorial and it's a bit outdated, so I'm trying to fill in the gaps. It says to use a BlobAttribute to set the filename, but I keep getting an error saying that the type or namespace isn't found.

I'm using CSX and I can't for the life of me get it to work. When I copy the line into a C# test function app, it worked just fine. I don't want to switch to that route right now because it's not part of the tutorial and I'm trying to stick with their flow, but they don't explain this either. The Microsoft.Azure.WebJobs using statements were mainly just me experimenting trying to get it to work.

Any ideas how to get the BlobAttribute to work in CSX?

#r "Newtonsoft.Json"
#r "Microsoft.Azure.WebJobs"
#r "Microsoft.Azure.WebJobs.Extensions"

using System;
using Newtonsoft.Json;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions;

public class Order
{
public string OrderID {get;set;}
public string ProductID {get;set;}
public string Email{get;set;}
public decimal Price {get;set;}
}

public static void Run(Order myQueueItem, ILogger log, IBinder binder)
{    
log.LogInformation($"C# Queue trigger function processed: 
{myQueueItem.OrderID}");

using(var outputBlob = binder.Bind<TextWriter>(new BlobAttribute($"{myQueueItem.OrderID}.lic")))    
{
    outputBlob.WriteLine($"OrderID: {myQueueItem.OrderID}");
    outputBlob.WriteLine($"ProductID: {myQueueItem.ProductID}");
    outputBlob.WriteLine($"Email: {myQueueItem.Email}");
    outputBlob.WriteLine($"Price: {myQueueItem.Price}");
    outputBlob.WriteLine($"Purchase Date: {DateTime.UtcNow}");

    var md5 = System.Security.Cryptography.MD5.Create();
    var hash = md5.ComputeHash(System.Text.Encoding.UTF8.GetBytes(myQueueItem.Email + "secret"));
    outputBlob.WriteLine($"Secret Code: 
{BitConverter.ToString(hash).Replace("-","")}");
    }
}