Add vendor supply categories with inventory auto-filter

Vendors can now be tagged with one or more inventory categories (Powder,
Chemical, etc.) via checkboxes on the Create/Edit form. The inventory
Create/Edit vendor dropdown automatically filters to matching vendors when
a category is selected; falls back to all vendors if none are tagged.
Includes migration AddVendorCategories (VendorInventoryCategories join table).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Application/DTOs/Vendor/VendorDtos.cs

@@ -125,6 +125,8 @@ public class CreateVendorDto
 
     [Display(Name = "Default Expense Account")]
     public int? DefaultExpenseAccountId { get; set; }
+
+    public List<int> CategoryIds { get; set; } = new();
 }
 
 // ============================================================================
@@ -209,4 +211,6 @@ public class UpdateVendorDto
 
     [Display(Name = "Default Expense Account")]
     public int? DefaultExpenseAccountId { get; set; }
+
+    public List<int> CategoryIds { get; set; } = new();
 }

src/PowderCoating.Core/Entities/InventoryCategoryLookup.cs

@@ -12,4 +12,5 @@ public class InventoryCategoryLookup : BaseEntity
 
     // Relationships
     public virtual ICollection<InventoryItem> InventoryItems { get; set; } = new List<InventoryItem>();
+    public virtual ICollection<Vendor> Vendors { get; set; } = new List<Vendor>();
 }

src/PowderCoating.Core/Entities/SupportingEntities.cs

@@ -45,6 +45,7 @@ public class Vendor : BaseEntity
     public virtual ICollection<BillPayment> BillPayments { get; set; } = new List<BillPayment>();
     public virtual ICollection<Expense> Expenses { get; set; } = new List<Expense>();
     public virtual Account? DefaultExpenseAccount { get; set; }
+    public virtual ICollection<InventoryCategoryLookup> Categories { get; set; } = new List<InventoryCategoryLookup>();
 }
 
 public class InventoryTransaction : BaseEntity

src/PowderCoating.Infrastructure/Data/ApplicationDbContext.cs

@@ -809,6 +809,15 @@ modelBuilder.Entity<ReworkRecord>().HasQueryFilter(e =>
             .HasForeignKey(s => s.DefaultExpenseAccountId)
             .OnDelete(DeleteBehavior.SetNull);
 
+        // Vendor ↔ InventoryCategoryLookup (many-to-many supply categories)
+        modelBuilder.Entity<Vendor>()
+            .HasMany(v => v.Categories)
+            .WithMany(c => c.Vendors)
+            .UsingEntity<Dictionary<string, object>>(
+                "VendorInventoryCategories",
+                j => j.HasOne<InventoryCategoryLookup>().WithMany().HasForeignKey("InventoryCategoryLookupId"),
+                j => j.HasOne<Vendor>().WithMany().HasForeignKey("VendorId"));
+
         // Bill → APAccount (no cascade to avoid cycles)
         modelBuilder.Entity<Bill>()
             .HasOne(b => b.APAccount)

src/PowderCoating.Infrastructure/Migrations/20260523135110_AddVendorCategories.cs

@@ -0,0 +1,93 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace PowderCoating.Infrastructure.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddVendorCategories : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "VendorInventoryCategories",
+                columns: table => new
+                {
+                    InventoryCategoryLookupId = table.Column<int>(type: "int", nullable: false),
+                    VendorId = table.Column<int>(type: "int", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_VendorInventoryCategories", x => new { x.InventoryCategoryLookupId, x.VendorId });
+                    table.ForeignKey(
+                        name: "FK_VendorInventoryCategories_InventoryCategoryLookups_InventoryCategoryLookupId",
+                        column: x => x.InventoryCategoryLookupId,
+                        principalTable: "InventoryCategoryLookups",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_VendorInventoryCategories_Vendors_VendorId",
+                        column: x => x.VendorId,
+                        principalTable: "Vendors",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.UpdateData(
+                table: "PricingTiers",
+                keyColumn: "Id",
+                keyValue: 1,
+                column: "CreatedAt",
+                value: new DateTime(2026, 5, 23, 13, 51, 6, 293, DateTimeKind.Utc).AddTicks(4300));
+
+            migrationBuilder.UpdateData(
+                table: "PricingTiers",
+                keyColumn: "Id",
+                keyValue: 2,
+                column: "CreatedAt",
+                value: new DateTime(2026, 5, 23, 13, 51, 6, 293, DateTimeKind.Utc).AddTicks(4313));
+
+            migrationBuilder.UpdateData(
+                table: "PricingTiers",
+                keyColumn: "Id",
+                keyValue: 3,
+                column: "CreatedAt",
+                value: new DateTime(2026, 5, 23, 13, 51, 6, 293, DateTimeKind.Utc).AddTicks(4315));
+
+            migrationBuilder.CreateIndex(
+                name: "IX_VendorInventoryCategories_VendorId",
+                table: "VendorInventoryCategories",
+                column: "VendorId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "VendorInventoryCategories");
+
+            migrationBuilder.UpdateData(
+                table: "PricingTiers",
+                keyColumn: "Id",
+                keyValue: 1,
+                column: "CreatedAt",
+                value: new DateTime(2026, 5, 21, 14, 32, 24, 337, DateTimeKind.Utc).AddTicks(8533));
+
+            migrationBuilder.UpdateData(
+                table: "PricingTiers",
+                keyColumn: "Id",
+                keyValue: 2,
+                column: "CreatedAt",
+                value: new DateTime(2026, 5, 21, 14, 32, 24, 337, DateTimeKind.Utc).AddTicks(8542));
+
+            migrationBuilder.UpdateData(
+                table: "PricingTiers",
+                keyColumn: "Id",
+                keyValue: 3,
+                column: "CreatedAt",
+                value: new DateTime(2026, 5, 21, 14, 32, 24, 337, DateTimeKind.Utc).AddTicks(8543));
+        }
+    }
+}

src/PowderCoating.Infrastructure/Migrations/ApplicationDbContextModelSnapshot.cs

@@ -6711,7 +6711,7 @@ namespace PowderCoating.Infrastructure.Migrations
                         {
                             Id = 1,
                             CompanyId = 0,
-                            CreatedAt = new DateTime(2026, 5, 21, 14, 32, 24, 337, DateTimeKind.Utc).AddTicks(8533),
+                            CreatedAt = new DateTime(2026, 5, 23, 13, 51, 6, 293, DateTimeKind.Utc).AddTicks(4300),
                             Description = "Standard pricing for regular customers",
                             DiscountPercent = 0m,
                             IsActive = true,
@@ -6722,7 +6722,7 @@ namespace PowderCoating.Infrastructure.Migrations
                         {
                             Id = 2,
                             CompanyId = 0,
-                            CreatedAt = new DateTime(2026, 5, 21, 14, 32, 24, 337, DateTimeKind.Utc).AddTicks(8542),
+                            CreatedAt = new DateTime(2026, 5, 23, 13, 51, 6, 293, DateTimeKind.Utc).AddTicks(4313),
                             Description = "5% discount for preferred customers",
                             DiscountPercent = 5m,
                             IsActive = true,
@@ -6733,7 +6733,7 @@ namespace PowderCoating.Infrastructure.Migrations
                         {
                             Id = 3,
                             CompanyId = 0,
-                            CreatedAt = new DateTime(2026, 5, 21, 14, 32, 24, 337, DateTimeKind.Utc).AddTicks(8543),
+                            CreatedAt = new DateTime(2026, 5, 23, 13, 51, 6, 293, DateTimeKind.Utc).AddTicks(4315),
                             Description = "10% discount for premium customers",
                             DiscountPercent = 10m,
                             IsActive = true,
@@ -8634,6 +8634,21 @@ namespace PowderCoating.Infrastructure.Migrations
                     b.ToTable("YearEndCloses");
                 });
 
+            modelBuilder.Entity("VendorInventoryCategories", b =>
+                {
+                    b.Property<int>("InventoryCategoryLookupId")
+                        .HasColumnType("int");
+
+                    b.Property<int>("VendorId")
+                        .HasColumnType("int");
+
+                    b.HasKey("InventoryCategoryLookupId", "VendorId");
+
+                    b.HasIndex("VendorId");
+
+                    b.ToTable("VendorInventoryCategories");
+                });
+
             modelBuilder.Entity("Microsoft.AspNetCore.Identity.IdentityRoleClaim<string>", b =>
                 {
                     b.HasOne("Microsoft.AspNetCore.Identity.IdentityRole", null)
@@ -10372,6 +10387,21 @@ namespace PowderCoating.Infrastructure.Migrations
                     b.Navigation("JournalEntry");
                 });
 
+            modelBuilder.Entity("VendorInventoryCategories", b =>
+                {
+                    b.HasOne("PowderCoating.Core.Entities.InventoryCategoryLookup", null)
+                        .WithMany()
+                        .HasForeignKey("InventoryCategoryLookupId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("PowderCoating.Core.Entities.Vendor", null)
+                        .WithMany()
+                        .HasForeignKey("VendorId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
             modelBuilder.Entity("PowderCoating.Core.Entities.Account", b =>
                 {
                     b.Navigation("BillLineItems");

src/PowderCoating.Web/Controllers/InventoryController.cs

@@ -1495,8 +1495,20 @@ public class InventoryController : Controller
         var companyId = _tenantContext.GetCurrentCompanyId() ?? 0;
         ViewBag.AiInventoryAssistEnabled = await _subscriptionService.IsAiInventoryAssistEnabledAsync(companyId);
 
-        var vendors = await _unitOfWork.Vendors.FindAsync(v => v.CompanyId == companyId);
-        ViewBag.Vendors = new SelectList(vendors.Where(s => s.IsActive).OrderBy(s => s.CompanyName), "Id", "CompanyName");
+        var vendors = (await _unitOfWork.Vendors.FindAsync(v => v.IsActive, false, v => v.Categories))
+            .OrderBy(v => v.CompanyName).ToList();
+        ViewBag.Vendors = new SelectList(vendors, "Id", "CompanyName");
+
+        // Build {categoryId: [vendorId, ...]} so the inventory form can filter vendors by category
+        var categoryVendorMap = new Dictionary<string, List<int>>();
+        foreach (var v in vendors)
+            foreach (var cat in v.Categories)
+            {
+                var key = cat.Id.ToString();
+                if (!categoryVendorMap.ContainsKey(key)) categoryVendorMap[key] = new List<int>();
+                categoryVendorMap[key].Add(v.Id);
+            }
+        ViewBag.CategoryVendorMapJson = System.Text.Json.JsonSerializer.Serialize(categoryVendorMap);
 
         // Load categories from lookup table
         var allCategories = await _unitOfWork.InventoryCategoryLookups.FindAsync(c => c.CompanyId == companyId);

src/PowderCoating.Web/Controllers/VendorsController.cs

@@ -181,6 +181,7 @@ public class VendorsController : Controller
     public async Task<IActionResult> Create(bool inline = false)
     {
         await PopulateExpenseAccountsAsync();
+        await PopulateVendorCategoriesAsync();
         if (inline)
             return PartialView(new CreateVendorDto());
         return View(new CreateVendorDto());
@@ -207,6 +208,7 @@ public class VendorsController : Controller
                 return Json(new { success = false, errors });
             }
             await PopulateExpenseAccountsAsync();
+            await PopulateVendorCategoriesAsync(dto.CategoryIds);
             return View(dto);
         }
 
@@ -216,6 +218,12 @@ public class VendorsController : Controller
             var vendor = _mapper.Map<Vendor>(dto);
             vendor.CompanyId = currentUser!.CompanyId;
 
+            if (dto.CategoryIds.Any())
+            {
+                var cats = await _unitOfWork.InventoryCategoryLookups.FindAsync(c => dto.CategoryIds.Contains(c.Id));
+                vendor.Categories = cats.ToList();
+            }
+
             await _unitOfWork.Vendors.AddAsync(vendor);
             await _unitOfWork.CompleteAsync();
 
@@ -247,14 +255,16 @@ public class VendorsController : Controller
 
         try
         {
-            var vendor = await _unitOfWork.Vendors.GetByIdAsync(id.Value);
+            var vendor = await _unitOfWork.Vendors.GetByIdAsync(id.Value, false, v => v.Categories);
             if (vendor == null)
             {
                 return NotFound();
             }
 
             var dto = _mapper.Map<UpdateVendorDto>(vendor);
+            dto.CategoryIds = vendor.Categories.Select(c => c.Id).ToList();
             await PopulateExpenseAccountsAsync();
+            await PopulateVendorCategoriesAsync(dto.CategoryIds);
             return View(dto);
         }
         catch (Exception ex)
@@ -282,18 +292,27 @@ public class VendorsController : Controller
         if (!ModelState.IsValid)
         {
             await PopulateExpenseAccountsAsync();
+            await PopulateVendorCategoriesAsync(dto.CategoryIds);
             return View(dto);
         }
 
         try
         {
-            var vendor = await _unitOfWork.Vendors.GetByIdAsync(id);
+            var vendor = await _unitOfWork.Vendors.GetByIdAsync(id, false, v => v.Categories);
             if (vendor == null)
             {
                 return NotFound();
             }
 
             _mapper.Map(dto, vendor);
+
+            vendor.Categories.Clear();
+            if (dto.CategoryIds.Any())
+            {
+                var cats = await _unitOfWork.InventoryCategoryLookups.FindAsync(c => dto.CategoryIds.Contains(c.Id));
+                foreach (var cat in cats) vendor.Categories.Add(cat);
+            }
+
             await _unitOfWork.Vendors.UpdateAsync(vendor);
             await _unitOfWork.CompleteAsync();
 
@@ -413,6 +432,20 @@ public class VendorsController : Controller
     /// purchases) in addition to regular operating expenses. A "— None —" placeholder is prepended so
     /// the field is optional — not every vendor needs a default account pre-set.
     /// </summary>
+    /// <summary>
+    /// Populates ViewBag.VendorCategories with active inventory categories for the checkbox list,
+    /// and ViewBag.SelectedCategoryIds with the IDs already assigned to the vendor being edited.
+    /// </summary>
+    private async Task PopulateVendorCategoriesAsync(IEnumerable<int>? selectedIds = null)
+    {
+        var companyId = (await _userManager.GetUserAsync(User))!.CompanyId;
+        var cats = (await _unitOfWork.InventoryCategoryLookups.FindAsync(c => c.CompanyId == companyId && c.IsActive))
+            .OrderBy(c => c.DisplayOrder)
+            .ToList();
+        ViewBag.VendorCategories = cats;
+        ViewBag.SelectedCategoryIds = (selectedIds ?? Enumerable.Empty<int>()).ToHashSet();
+    }
+
     private async Task PopulateExpenseAccountsAsync()
     {
         var accounts = (await _unitOfWork.Accounts.FindAsync(

src/PowderCoating.Web/Views/Inventory/Create.cshtml

@@ -345,6 +345,10 @@
                                     <option value="">Select vendor</option>
                                     <option value="__new__">+ Add New Vendor&hellip;</option>
                                 </select>
+                                <div id="vendor-filter-note" class="form-text d-none">
+                                    <i class="bi bi-funnel me-1 text-info"></i><span class="text-info">Showing vendors for this category.</span>
+                                    <a href="#" id="vendor-filter-clear" class="ms-1">Show all</a>
+                                </div>
                                 <span asp-validation-for="PrimaryVendorId" class="text-danger"></span>
                             </div>
                         </div>
@@ -438,4 +442,38 @@
     {
         <script src="~/js/inventory-label-scan.js"></script>
     }
+    <script>
+    (function () {
+        const categoryVendorMap = @Html.Raw(ViewBag.CategoryVendorMapJson ?? "{}");
+        const vendorSelect = document.getElementById('field-vendor');
+        const allVendorOptions = Array.from(vendorSelect.options).map(o => ({ v: o.value, t: o.text }));
+
+        function filterVendors(catId, forceAll) {
+            const vendorIds = (!forceAll && catId) ? (categoryVendorMap[catId] || []) : [];
+            const isFiltered = vendorIds.length > 0;
+            const currentVal = vendorSelect.value;
+
+            vendorSelect.innerHTML = '';
+            allVendorOptions.forEach(function (opt) {
+                if (!isFiltered || !opt.v || opt.v === '__new__' || vendorIds.includes(Number(opt.v)))
+                    vendorSelect.add(new Option(opt.t, opt.v));
+            });
+
+            if (Array.from(vendorSelect.options).some(o => o.value === currentVal))
+                vendorSelect.value = currentVal;
+
+            document.getElementById('vendor-filter-note').classList.toggle('d-none', !isFiltered);
+        }
+
+        document.getElementById('field-category').addEventListener('change', function () {
+            filterVendors(this.value, false);
+        });
+        document.getElementById('vendor-filter-clear')?.addEventListener('click', function (e) {
+            e.preventDefault();
+            filterVendors(document.getElementById('field-category').value, true);
+        });
+
+        filterVendors(document.getElementById('field-category').value, false);
+    })();
+    </script>
 }

src/PowderCoating.Web/Views/Inventory/Edit.cshtml

@@ -341,6 +341,10 @@
                                     <option value="">Select vendor</option>
                                     <option value="__new__">+ Add New Vendor&hellip;</option>
                                 </select>
+                                <div id="vendor-filter-note" class="form-text d-none">
+                                    <i class="bi bi-funnel me-1 text-info"></i><span class="text-info">Showing vendors for this category.</span>
+                                    <a href="#" id="vendor-filter-clear" class="ms-1">Show all</a>
+                                </div>
                                 <span asp-validation-for="PrimaryVendorId" class="text-danger"></span>
                             </div>
                             <div class="col-12">
@@ -457,4 +461,39 @@
     {
         <script src="~/js/inventory-label-scan.js"></script>
     }
+    <script>
+    (function () {
+        const categoryVendorMap = @Html.Raw(ViewBag.CategoryVendorMapJson ?? "{}");
+        const vendorSelect = document.getElementById('field-vendor');
+        const allVendorOptions = Array.from(vendorSelect.options).map(o => ({ v: o.value, t: o.text }));
+
+        function filterVendors(catId, forceAll) {
+            const vendorIds = (!forceAll && catId) ? (categoryVendorMap[catId] || []) : [];
+            const isFiltered = vendorIds.length > 0;
+            const currentVal = vendorSelect.value;
+
+            vendorSelect.innerHTML = '';
+            allVendorOptions.forEach(function (opt) {
+                if (!isFiltered || !opt.v || opt.v === '__new__' || vendorIds.includes(Number(opt.v)))
+                    vendorSelect.add(new Option(opt.t, opt.v));
+            });
+
+            if (Array.from(vendorSelect.options).some(o => o.value === currentVal))
+                vendorSelect.value = currentVal;
+
+            document.getElementById('vendor-filter-note').classList.toggle('d-none', !isFiltered);
+        }
+
+        document.getElementById('field-category').addEventListener('change', function () {
+            filterVendors(this.value, false);
+        });
+        document.getElementById('vendor-filter-clear')?.addEventListener('click', function (e) {
+            e.preventDefault();
+            filterVendors(document.getElementById('field-category').value, true);
+        });
+
+        // Apply on load — Edit already has a category selected
+        filterVendors(document.getElementById('field-category').value, false);
+    })();
+    </script>
 }

src/PowderCoating.Web/Views/Vendors/Create.cshtml

@@ -195,6 +195,27 @@
                         </div>
                     </div>
 
+                    <!-- Supply Categories -->
+                    @if (ViewBag.VendorCategories is IEnumerable<PowderCoating.Core.Entities.InventoryCategoryLookup> cats && cats.Any())
+                    {
+                    <div class="mb-4">
+                        <h5 class="border-bottom pb-2 mb-3">
+                            <i class="bi bi-tags me-2 text-primary"></i>Supply Categories
+                        </h5>
+                        <div class="d-flex flex-wrap gap-3">
+                            @foreach (var cat in cats)
+                            {
+                                <div class="form-check">
+                                    <input class="form-check-input" type="checkbox"
+                                           name="CategoryIds" value="@cat.Id" id="cat_@cat.Id" />
+                                    <label class="form-check-label" for="cat_@cat.Id">@cat.DisplayName</label>
+                                </div>
+                            }
+                        </div>
+                        <div class="form-text">Tag this vendor with the types of supplies they provide. Used to filter the vendor list when adding inventory items.</div>
+                    </div>
+                    }
+
                     <!-- Notes Section -->
                     <div class="mb-4">
                         <h5 class="border-bottom pb-2 mb-3">

src/PowderCoating.Web/Views/Vendors/Edit.cshtml

@@ -198,6 +198,29 @@
                         </div>
                     </div>
 
+                    <!-- Supply Categories -->
+                    @if (ViewBag.VendorCategories is IEnumerable<PowderCoating.Core.Entities.InventoryCategoryLookup> cats && cats.Any())
+                    {
+                    var selectedCatIds = (HashSet<int>)ViewBag.SelectedCategoryIds;
+                    <div class="mb-4">
+                        <h5 class="border-bottom pb-2 mb-3">
+                            <i class="bi bi-tags me-2 text-primary"></i>Supply Categories
+                        </h5>
+                        <div class="d-flex flex-wrap gap-3">
+                            @foreach (var cat in cats)
+                            {
+                                <div class="form-check">
+                                    <input class="form-check-input" type="checkbox"
+                                           name="CategoryIds" value="@cat.Id" id="cat_@cat.Id"
+                                           @(selectedCatIds.Contains(cat.Id) ? "checked" : "") />
+                                    <label class="form-check-label" for="cat_@cat.Id">@cat.DisplayName</label>
+                                </div>
+                            }
+                        </div>
+                        <div class="form-text">Tag this vendor with the types of supplies they provide. Used to filter the vendor list when adding inventory items.</div>
+                    </div>
+                    }
+
                     <!-- Notes Section -->
                     <div class="mb-4">
                         <h5 class="border-bottom pb-2 mb-3">