Добавил модель Supplier

Store/Controllers/ProductController.cs

+using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
 using Store.Models;
 
 namespace Store.Controllers
@@ -20,16 +22,21 @@ namespace Store.Controllers
 
         public IActionResult Details(string id)
         {
-            Product product = _context.Products.FirstOrDefault(p => p.Id == id);
+            Product product = _context.Products
+                .Include(p => p.Supplier)
+                .First(p => p.Id.ToString() == id);
+
             ViewBag.product = product;
+            ViewBag.supplier = product.Supplier;
             return View();
         }
 
-        [ActionName("CreateProduct")]
         [HttpGet]
         public IActionResult Create()
         {
-            return View();
+            List<Supplier> suppliers = _context.Suppliers.ToList();
+            ViewBag.suppliers = suppliers;
+            return View(new Product());
         }
 
         [HttpPost]

Store/Migrations/20190605141259_AddSuppliersTable.Designer.cs

+// <auto-generated />
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+using Store.Models;
+
+namespace Store.Migrations
+{
+    [DbContext(typeof(ProductContext))]
+    [Migration("20190605141259_AddSuppliersTable")]
+    partial class AddSuppliersTable
+    {
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.SerialColumn)
+                .HasAnnotation("ProductVersion", "2.2.4-servicing-10062")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            modelBuilder.Entity("Store.Models.Product", b =>
+                {
+                    b.Property<string>("Id")
+                        .ValueGeneratedOnAdd();
+
+                    b.Property<int>("Amount");
+
+                    b.Property<string>("Brand");
+
+                    b.Property<string>("Category");
+
+                    b.Property<string>("Description");
+
+                    b.Property<string>("Name");
+
+                    b.Property<string>("SupplierId");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("SupplierId");
+
+                    b.ToTable("Products");
+                });
+
+            modelBuilder.Entity("Store.Models.Supplier", b =>
+                {
+                    b.Property<string>("Id")
+                        .ValueGeneratedOnAdd();
+
+                    b.Property<string>("Name");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Supplier");
+                });
+
+            modelBuilder.Entity("Store.Models.Product", b =>
+                {
+                    b.HasOne("Store.Models.Supplier", "Supplier")
+                        .WithMany("Products")
+                        .HasForeignKey("SupplierId");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

Store/Migrations/20190605141259_AddSuppliersTable.cs

+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace Store.Migrations
+{
+    public partial class AddSuppliersTable : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "SupplierId",
+                table: "Products",
+                nullable: true);
+
+            migrationBuilder.CreateTable(
+                name: "Suppliers",
+                columns: table => new
+                {
+                    Id = table.Column<string>(nullable: false),
+                    Name = table.Column<string>(nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Supplier", x => x.Id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Products_SupplierId",
+                table: "Products",
+                column: "SupplierId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Products_Supplier_SupplierId",
+                table: "Products",
+                column: "SupplierId",
+                principalTable: "Suppliers",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.Restrict);
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Products_Supplier_SupplierId",
+                table: "Products");
+
+            migrationBuilder.DropTable(
+                name: "Suppliers");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Products_SupplierId",
+                table: "Products");
+
+            migrationBuilder.DropColumn(
+                name: "SupplierId",
+                table: "Products");
+        }
+    }
+}

Store/Migrations/ProductContextModelSnapshot.cs

 // <auto-generated />
+using System;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
@@ -33,10 +34,33 @@ namespace Store.Migrations
 
                     b.Property<string>("Name");
 
+                    b.Property<string>("SupplierId");
+
                     b.HasKey("Id");
 
+                    b.HasIndex("SupplierId");
+
                     b.ToTable("Products");
                 });
+
+            modelBuilder.Entity("Store.Models.Supplier", b =>
+                {
+                    b.Property<string>("Id")
+                        .ValueGeneratedOnAdd();
+
+                    b.Property<string>("Name");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Suppliers");
+                });
+
+            modelBuilder.Entity("Store.Models.Product", b =>
+                {
+                    b.HasOne("Store.Models.Supplier", "Supplier")
+                        .WithMany("Products")
+                        .HasForeignKey("SupplierId");
+                });
 #pragma warning restore 612, 618
         }
     }

Store/Models/Product.cs

+using System;
+
 namespace Store.Models
 {
     public class Product
@@ -8,5 +10,8 @@ namespace Store.Models
         public string Brand { get; set; }
         public int Amount { get; set; }
         public string Description { get; set; }
+
+        public string SupplierId { get; set; }
+        public virtual Supplier Supplier { get; set; }
     }
 }

Store/Models/ProductContext.cs

@@ -5,6 +5,7 @@ namespace Store.Models
     public class ProductContext : DbContext
     {
         public DbSet<Product> Products { get; set; }
+        public DbSet<Supplier> Suppliers { get; set; }
 
         public ProductContext(DbContextOptions<ProductContext> options) :
             base(options)

Store/Models/Supplier.cs

+using System.Collections.Generic;
+
+namespace Store.Models
+{
+    public class Supplier
+    {
+        public string Id { get; set; }
+        public string Name { get; set; }
+
+        public virtual ICollection<Product> Products { get; set; }
+    }
+}

Store/Startup.cs

@@ -29,7 +29,8 @@ namespace Store
             });
 
             string connection = Configuration.GetConnectionString("StoreConnection");
-            services.AddDbContext<ProductContext>(options => options.UseNpgsql(connection));
+            services.AddDbContext<ProductContext>(options => options
+                .UseNpgsql(connection));
 
             services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
         }

Store/Store.csproj

@@ -6,7 +6,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="EntityFramework" Version="6.1.3" />
     <PackageReference Include="Microsoft.AspNetCore" Version="2.1.2" />
     <PackageReference Include="Microsoft.AspNetCore.CookiePolicy" Version="2.1.1" />
     <PackageReference Include="Microsoft.AspNetCore.HttpsPolicy" Version="2.1.1" />

Store/Views/Product/CreateProduct.cshtml → Store/Views/Product/Create.cshtml

+@using Store.Models
 @model Store.Models.Product
 @{
     Layout = "_MainLayout";
@@ -32,6 +33,16 @@
     <input type="text" class="form-control" value="@Model.Description" id="Description" name="Description" placeholder="Enter amount">
   </div>
 
+  <div class="form-group">
+    <label for="">Supplier</label>
+    <select name="SupplierId">
+      @foreach (Supplier s in ViewBag.suppliers)
+      {
+        <option value="@s.Id">@s.Name</option>
+      }
+    </select>
+  </div>
+
   <button type="submit" class="btn btn-primary">Create</button>
 </form>
 

Store/Views/Product/Details.cshtml

@@ -21,5 +21,9 @@
         <td>Amount:</td>
         <td>@ViewBag.product.Amount</td>
     </tr>
+    <tr>
+        <td>Supplier Name:</td>
+        <td>@ViewBag.supplier.Name</td>
+    </tr>
     </tbody>
 </table>