решаем конфликты

ComputerHardwareStore/ComputerHardwareStore.sln

@@ -9,7 +9,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ComputerHardwareStoreDataMo
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ComputerHardwareStoreContracts", "ComputerHardwareStoreContracts\ComputerHardwareStoreContracts.csproj", "{5F394E21-2597-432B-AE73-BBAFD8D9F50E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ComputerHardwareStoreBusinessLogic", "ComputerHardwareStoreBusinessLogic\ComputerHardwareStoreBusinessLogic.csproj", "{D32DEB60-AF40-46AF-8914-DC6A19BD66CD}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ComputerHardwareStoreBusinessLogic", "ComputerHardwareStoreBusinessLogic\ComputerHardwareStoreBusinessLogic.csproj", "{D32DEB60-AF40-46AF-8914-DC6A19BD66CD}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ComputerHardwareStoreDatabaseImplement", "ComputerHardwareStoreDatabaseImplement\ComputerHardwareStoreDatabaseImplement.csproj", "{09A57BE9-A653-4AAD-9FB2-1F8974F294CD}"
 EndProject
@@ -35,10 +35,6 @@ Global
 		{D32DEB60-AF40-46AF-8914-DC6A19BD66CD}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D32DEB60-AF40-46AF-8914-DC6A19BD66CD}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D32DEB60-AF40-46AF-8914-DC6A19BD66CD}.Release|Any CPU.Build.0 = Release|Any CPU
-		{09A57BE9-A653-4AAD-9FB2-1F8974F294CD}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{09A57BE9-A653-4AAD-9FB2-1F8974F294CD}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{09A57BE9-A653-4AAD-9FB2-1F8974F294CD}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{09A57BE9-A653-4AAD-9FB2-1F8974F294CD}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

ComputerHardwareStore/ComputerHardwareStoreContracts/BindingModels/OrderBindingModel.cs

@@ -10,6 +10,6 @@ namespace ComputerHardwareStoreContracts.BindingModels
         public OrderStatus Status { get; set; } = OrderStatus.Неизвестен;
         public DateTime DateCreate { get; set; } = DateTime.Now;
         public DateTime? DateImplement { get; set; } = null;
-        public Dictionary<int, (IProductModel, int)> OrderProduct { get; set; } = new();
+        public Dictionary<int, (IProductModel, int)> OrderProducts { get; set; } = new();
     }
 }

ComputerHardwareStore/ComputerHardwareStoreContracts/ViewModels/OrderViewModel.cs

@@ -16,6 +16,6 @@ namespace ComputerHardwareStoreContracts.ViewModels
         public DateTime DateCreate { get; set; }
         [DisplayName("Дата выполнения")]
         public DateTime? DateImplement { get; set; }
-        public Dictionary<int, (IProductModel, int)> OrderProduct { get; set; } = new();
+        public Dictionary<int, (IProductModel, int)> OrderProducts { get; set; } = new();
     }
 }

ComputerHardwareStore/ComputerHardwareStoreDataModels/Models/IOrderModel.cs

@@ -8,6 +8,6 @@ namespace ComputerHardwareStoreDataModels.Models
         OrderStatus Status { get; }
         DateTime DateCreate { get; }
         DateTime? DateImplement { get; }
-        public Dictionary<int, (IProductModel, int)> OrderProduct { get; }
+        public Dictionary<int, (IProductModel, int)> OrderProducts { get; }
     }
 }

ComputerHardwareStore/ComputerHardwareStoreDatabaseImplement/ComputerHardwareStoreDBContext.cs

@@ -34,5 +34,6 @@ namespace ComputerHardwareStoreDatabaseImplement
 
         public virtual DbSet<StoreKeeper> StoreKeepers { set; get; }
         public virtual DbSet<Build> Builds { set; get; }
+        public virtual DbSet<OrderProduct> OrderProducts { set; get; }
     }
 }

ComputerHardwareStore/ComputerHardwareStoreDatabaseImplement/Models/Order.cs

@@ -3,6 +3,7 @@ using ComputerHardwareStoreContracts.ViewModels;
 using ComputerHardwareStoreDataModels.Enums;
 using ComputerHardwareStoreDataModels.Models;
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 
 namespace ComputerHardwareStoreDatabaseImplement.Models
 {
@@ -18,9 +19,25 @@ namespace ComputerHardwareStoreDatabaseImplement.Models
         [Required]
         public DateTime DateCreate { get; set; } = DateTime.Now;
         public DateTime? DateImplement { get; set; }
-        [Required]
-        public int ProductId { get; private set; }
-        public virtual Product? Product { get; set; }
+
+        private Dictionary<int, (IProductModel, int)>? _orderProducts = null;
+        [NotMapped]
+        public Dictionary<int, (IProductModel, int)> OrderProducts 
+        {
+            get
+            {
+                if (_orderProducts == null)
+                {
+                    _orderProducts = Products
+                        .ToDictionary(
+                            op => op.ProductId, 
+                            op => (op.Product as IProductModel, op.Count));
+                }
+                return _orderProducts;
+            }
+        }
+        [ForeignKey("OrderId")]
+        public virtual List<OrderProduct> Products { get; set; } = new();
         public static Order? Create(ComputerHardwareStoreDBContext context, OrderBindingModel model)
         {
             if (model == null)
@@ -34,7 +51,14 @@ namespace ComputerHardwareStoreDatabaseImplement.Models
                 Status = model.Status,
                 DateCreate = model.DateCreate,
                 DateImplement = model.DateImplement,
-                Product = context.Products.First(x => x.Id == model.ProductId)
+                Products = model.OrderProducts
+                    .Select(op => new OrderProduct()
+                    {
+                        OrderId = model.Id,
+                        ProductId = op.Key,
+                        Count = op.Value.Item2
+                    })
+                    .ToList()
             };
         }
         public void Update(OrderBindingModel model)
@@ -57,3 +81,4 @@ namespace ComputerHardwareStoreDatabaseImplement.Models
 
         public Dictionary<int, (IProductModel, int)> OrderProduct => throw new NotImplementedException();
     }
+}

ComputerHardwareStore/ComputerHardwareStoreDatabaseImplement/Models/OrderProduct.cs

@@ -0,0 +1,17 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace ComputerHardwareStoreDatabaseImplement.Models
+{
+    public class OrderProduct
+    {
+        public int Id { get; set; }
+        [Required]
+        public int OrderId { get; set; }
+        [Required]
+        public int ProductId { get; set; }
+        [Required]
+        public int Count { get; set; }
+        public virtual Product Product { get; set; } = new();
+        public virtual Order Order { get; set; } = new();
+    }
+}