query error when using .Include / .ThenInclude

Hi,

Given the code below, can anyone tell me why there's the error?

Model
===================
    public partial class Issue1Transaction
    {
        public Issue1Transaction()
        {
            IssueDetails = new HashSet<IssueDetails>();
        }

        public long IssueTransactionId { get; set; }
        public DateTime IssueDate { get; set; }

        public virtual ICollection<IssueDetails> IssueDetails { get; set; }
    }

    public partial class IssueDetails
    {
        public long IssueDetailsId { get; set; }
        public long IssueTransactionId { get; set; }
        public long InventoryId { get; set; }
        public int Quantity { get; set; }

        public virtual Inventory Inventory { get; set; }
        public virtual Issue1Transaction IssueTransaction { get; set; }
    }

    public partial class Inventory
    {
        public Inventory()
        {
            IssueDetails = new HashSet<IssueDetails>();
            IssueTransaction = new HashSet<IssueTransaction>();
            Repair = new HashSet<Repair>();
            ReturnDetails = new HashSet<ReturnDetails>();
            ReturnTransaction = new HashSet<ReturnTransaction>();
        }

        public long InventoryId { get; set; }
        public string MaterialCode { get; set; }
        public string PropertyId { get; set; }
        public int Quantity { get; set; }
        public int? ToolRoomId { get; set; }

        public virtual Material MaterialCodeNavigation { get; set; }
        public virtual ToolRoom ToolRoom { get; set; }
        public virtual ICollection<IssueDetails> IssueDetails { get; set; }
        public virtual ICollection<IssueTransaction> IssueTransaction { get; set; }

    }

Business Logic
=====================

using System;
using System.Collections.Generic;
using System.Linq;
using ToolsOracle.Data;
using ToolsOracle.Data.Models;
using ToolsOracle.Data.ViewModel;
using Microsoft.EntityFrameworkCore;
using Microsoft.AspNetCore.Identity;

            var query1 = dbViews.Issue1Transaction
                                                .Include(item => item.IssueDetails)
                                                .ThenInclude(item => item.Inventory)
                                                    .ThenInclude(item => item.MaterialCodeNavigation)
                    .Where(item => item.IssueDetails.Inventory)  // => how come this errors out?  it's complaining

Error:

ICollection<IssueDetails> does not contain a definition for 'inv' and no extension method 'inv' accepting a first argument of type 'ICollection<IssueDetails>' could be found(are you missing a using directive or an assembly reference?)

Please advise.

Thanks,

tinac99