I have a PurchaseOrder model:

public class PurchaseOrder
{ 
    public string OrderNumber { get; set; }
    public string Customer { get; set; }
    public IList<LineItem> Lines { get; set; }
}

and a LineItem class:

public class LineItem
{ 
   public string PartNumber { get; set; }
   public int Quantity { get; set; }
}

What I want to do is on my view for the PurhcaseOrder Create action, I need a section for line items. The user should be able to add a new line, remove a line, then submit. One caveat is the PartNumber needs to be a dropdown list of valid parts.

What can I do to accomplish what I'm looking for?