i have added my part

entity/Product.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
+using static entity.SalesOrder;
 
 namespace entity
 {
@@ -52,67 +53,105 @@ public class SalesOrder
     {
         [Key]
         public int SalesOrderId { get; set; }
-=======
-    public class Order
-    {
-        [Key]
-        public int OrderId { get; set; }
-
+        public class Order
+        {
+            [Key]
+            public int OrderId { get; set; }
 
-        [Required]
-        public DateTime OrderDate { get; set; }
 
-
-        // Other sales order properties
+            [Required]
+            public DateTime OrderDate { get; set; }
 
-        public virtual ICollection<SalesOrderLineItem> SalesOrderLineItems { get; set; }
 
-        [ForeignKey("Customer")]
-        public int CustomerId { get; set; }
-        public virtual Customer Customer { get; set; }
+            // Other sales order properties
+
+            public virtual ICollection<SalesOrderLineItem> SalesOrderLineItems { get; set; }
+
+            [ForeignKey("Customer")]
+            public int CustomerId { get; set; }
+            public virtual Customer Customer { get; set; }
+        }
+
+        public class SalesOrderLineItem
+        {
+            [Key]
+            public int SalesOrderLineItemId { get; set; }
+            // Other order properties
+
+            public virtual ICollection<OrderLineItem> OrderLineItems { get; set; }
+        }
+
+        public class OrderLineItem
+        {
+            [Key]
+            public int OrderLineItemId { get; set; }
+
+
+            [Required]
+            public int Quantity { get; set; }
+
+            [Required]
+            public decimal UnitPrice { get; set; }
+
+            // Other sales order line item properties
+
+            [ForeignKey("SalesOrder")]
+            public int SalesOrderId { get; set; }
+            public virtual SalesOrder SalesOrder { get; set; }
+            // Other order line item properties
+
+            [ForeignKey("Order")]
+            public int OrderId { get; set; }
+            public virtual Order Order { get; set; }
+
+
+            [ForeignKey("Product")]
+            public int ProductId { get; set; }
+            public virtual Product Product { get; set; }
+        }
+
     }
 
-    public class SalesOrderLineItem
+    public class Purchase
     {
         [Key]
-        public int SalesOrderLineItemId { get; set; }
-=======
-        // Other order properties
+        public int PurchaseId { get; set; }
+
+        [Required]
+        public DateTime PurchaseDate { get; set; }
+
+        // Other purchase properties
 
-        public virtual ICollection<OrderLineItem> OrderLineItems { get; set; }
+        public virtual ICollection<PurchaseLineItem> PurchaseLineItems { get; set; }
+
+        [ForeignKey("Supplier")]
+        public int SupplierId { get; set; }
+        public virtual Supplier Supplier { get; set; }
     }
 
-    public class OrderLineItem
+    public class PurchaseLineItem
     {
         [Key]
-        public int OrderLineItemId { get; set; }
-
+        public int PurchaseLineItemId { get; set; }
 
         [Required]
         public int Quantity { get; set; }
 
         [Required]
         public decimal UnitPrice { get; set; }
 
-        // Other sales order line item properties
-
-        [ForeignKey("SalesOrder")]
-        public int SalesOrderId { get; set; }
-        public virtual SalesOrder SalesOrder { get; set; }
-=======
-        // Other order line item properties
-
-        [ForeignKey("Order")]
-        public int OrderId { get; set; }
-        public virtual Order Order { get; set; }
+        // Other purchase line item properties
 
+        [ForeignKey("Purchase")]
+        public int PurchaseId { get; set; }
+        public virtual Purchase Purchase { get; set; }
 
         [ForeignKey("Product")]
         public int ProductId { get; set; }
         public virtual Product Product { get; set; }
     }
-
 }
 
 
 
+