Getting userID in ASP.NET C# when posting item

Question

I am building a small craigslist/ebay type marketplace for my local community.

Most of the site is simple CRUD operations. I have enabled Individual user accounts and when someone posts an item to the marketplace I'd like to bind their current userID to the post. I have the fields set up but how can I automatically attach the logged in user's Id.

This is my product class

public class Product
{
    public string Title { get; set; }
    public decimal Price { get; set; }
    public string Photo { get; set; }
    public string Description { get; set; }
    public bool Availability { get; set; }
    public string Category { get; set; }

    public string Id { get; set; }

    public virtual ApplicationUser ApplicationUser { get; set; }
}

I have a field in the product database table that will hold the ApplicationUser_Id string value, but I do not know how to set it.

This is my create product controller. Would I put in that userID logic here?

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "Id,Title,Price,Description,Availability,Category,Photo")] Product product)
{
    if (ModelState.IsValid)
    {
        db.Products.Add(product);
        db.SaveChanges();
        return RedirectToAction("Index");
    }

    return View(product);
}

Answer 1

Yes, you would need to add the user to the product before you save it. Something like:

if (ModelState.IsValid)
{
    db.Products.Add(product);        
    db.Products.ApplicationUser = currentUser; //depending how you have your user defined       
    db.SaveChanges();
    return RedirectToAction("Index");
}

I haven't used Entity in awhile, so I think this should be correct