diff --git a/TinyPOS/TinyPosEntity/Entity/Product.cs b/TinyPOS/TinyPosEntity/Entity/Product.cs
new file mode 100644
index 0000000..bb0a718
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Entity/Product.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TinyPosEntity.Entity
+{
+    public class Product
+    {
+        public int ProductId { get; set; }
+
+        [MaxLength(450)]
+        [Index(IsUnique = true)]
+        public string Barcode { get; set; }
+
+        public ProductType ProductType { get; set; }
+
+        public string Name { get; set; }
+
+        public int Price { get; set; }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Entity/ProductType.cs b/TinyPOS/TinyPosEntity/Entity/ProductType.cs
new file mode 100644
index 0000000..594e0ad
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Entity/ProductType.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TinyPosEntity.Entity
+{
+    public class ProductType
+    {
+        public int ProductTypeId { get; set; }
+
+        [MaxLength(450)]
+        [Index(IsUnique = true)]
+        public string Name { get; set; }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Entity/Transaction.cs b/TinyPOS/TinyPosEntity/Entity/Transaction.cs
new file mode 100644
index 0000000..a858527
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Entity/Transaction.cs
@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TinyPosEntity.Entity
+{
+    public class Transaction
+    {
+        public string TransactionId { get; set; }
+
+        public DateTime Timestamp { get; set; }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Entity/TransactionItem.cs b/TinyPOS/TinyPosEntity/Entity/TransactionItem.cs
new file mode 100644
index 0000000..9bc35fb
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Entity/TransactionItem.cs
@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TinyPosEntity.Entity
+{
+    public class TransactionItem
+    {
+        public string TransactionItemId { get; set; }
+
+        public Transaction Transaction { get; set; }
+
+        public Product Product { get; set; }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Service/ProductService.cs b/TinyPOS/TinyPosEntity/Service/ProductService.cs
new file mode 100644
index 0000000..d4985ff
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Service/ProductService.cs
@@ -0,0 +1,136 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TinyPosEntity.Entity;
+
+namespace TinyPosEntity.Service
+{
+    public class ProductService
+    {
+        static ProductService instance;
+        public static ProductService Instance { get { Init(); return instance; } }
+
+        private static void Init()
+        {
+            if (instance == null)
+                instance = new ProductService();
+        }
+
+        public void Create(Product targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.Products.Add(targetObject);
+                context.SaveChanges();
+            }
+        }
+
+        public void Create(List<Product> targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                foreach (Product type in targetObject)
+                {
+                    context.Products.Add(type);
+                }
+
+                context.SaveChanges();
+            }
+        }
+
+        public Product Find(Product targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from p in context.Products
+                          where p.Name.Equals(targetObject.Barcode)
+                          select p;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToArray()[0];
+            }
+        }
+
+        public Product Find(string barcode)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from p in context.Products
+                          where p.Name.Equals(barcode)
+                          select p;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToArray()[0];
+            }
+        }
+
+        public List<Product> Find(List<TransactionItem> transactionItemList)
+        {
+            var subQry = from ti in transactionItemList
+                         select ti.Product.ProductId;
+
+            List<int> productIdList = subQry.ToList();
+            if (productIdList == null || productIdList.Count < 1)
+                return null;
+            
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from p in context.Products
+                          where productIdList.Contains(p.ProductId)
+                          orderby p.ProductId ascending
+                          select p;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToList();
+            }
+        }
+
+        public List<Product> Find(DateTime fromDateTime, DateTime toDateTime)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from p in context.Products
+                          join ti in context.TransactionItems
+                            on p equals ti.Product
+                          join t in context.Transactions
+                            on ti.Transaction equals t
+                          where (t.Timestamp >= fromDateTime && t.Timestamp <= toDateTime)
+                          orderby p.ProductId ascending
+                          select p;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToList();
+            }
+        }
+
+        public void Remove(Product targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.Database.ExecuteSqlCommand(
+                    "DELETE FROM dbo.Products WHERE ProductId = {0}",
+                    targetObject.ProductId);
+            }
+        }
+
+        public void Remove(string barcode)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.Database.ExecuteSqlCommand(
+                    "DELETE FROM dbo.Products WHERE Barcode = {0}",
+                    barcode);
+            }
+        }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Service/ProductTypeService.cs b/TinyPOS/TinyPosEntity/Service/ProductTypeService.cs
new file mode 100644
index 0000000..9af04c6
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Service/ProductTypeService.cs
@@ -0,0 +1,108 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TinyPosEntity.Entity;
+
+namespace TinyPosEntity.Service
+{
+    public class ProductTypeService
+    {
+        static ProductTypeService instance;
+        public static ProductTypeService Instance { get { Init(); return instance; } }
+
+        private static void Init()
+        {
+            if (instance == null)
+                instance = new ProductTypeService();
+        }
+
+        public void Create(ProductType targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.ProductTypes.Add(targetObject);
+                context.SaveChanges();
+            }
+        }
+
+        public void Create(List<ProductType> targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                foreach (ProductType type in targetObject)
+                {
+                    context.ProductTypes.Add(type);
+                }
+
+                context.SaveChanges();
+            }
+        }
+
+        public List<ProductType> FindAll()
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from pt in context.ProductTypes
+                          orderby pt.ProductTypeId ascending
+                          select pt;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToList();
+            }
+        }
+
+        public ProductType Find(ProductType targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from pt in context.ProductTypes
+                          where pt.Name.Equals(targetObject.Name)
+                          select pt;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToArray()[0];
+            }
+        }
+
+        public ProductType Find(string name)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from pt in context.ProductTypes
+                          where pt.Name.Equals(name)
+                          select pt;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToArray()[0];
+            }
+        }
+
+        public void Remove(ProductType targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.Database.ExecuteSqlCommand(
+                    "DELETE FROM dbo.Students WHERE ProductTypeId = {0}",
+                    targetObject.ProductTypeId);
+            }
+        }
+
+        public void Remove(string name)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.Database.ExecuteSqlCommand(
+                    "DELETE FROM dbo.Students WHERE Name = {0}",
+                    name);
+            }
+        }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Service/TransactionItemService.cs b/TinyPOS/TinyPosEntity/Service/TransactionItemService.cs
new file mode 100644
index 0000000..a34a69c
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Service/TransactionItemService.cs
@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TinyPosEntity.Entity;
+
+namespace TinyPosEntity.Service
+{
+    public class TransactionItemService
+    {
+        static TransactionItemService instance;
+        public static TransactionItemService Instance { get { Init(); return instance; } }
+
+        private static void Init()
+        {
+            if (instance == null)
+                instance = new TransactionItemService();
+        }
+
+        public void Create(TransactionItem targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.TransactionItems.Add(targetObject);
+                context.SaveChanges();
+            }
+        }
+
+        public void Create(List<TransactionItem> targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                foreach (TransactionItem type in targetObject)
+                {
+                    context.TransactionItems.Add(type);
+                }
+
+                context.SaveChanges();
+            }
+        }
+
+        public List<TransactionItem> Find(DateTime fromDateTime, DateTime toDateTime)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from ti in context.TransactionItems
+                          join t in context.Transactions
+                            on ti.Transaction equals t
+                          where (t.Timestamp >= fromDateTime && t.Timestamp <= toDateTime)
+                          orderby t.Timestamp descending
+                          select ti;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToList();
+            }
+        }
+    }
+}
diff --git a/TinyPOS/TinyPosEntity/Service/TransactionService.cs b/TinyPOS/TinyPosEntity/Service/TransactionService.cs
new file mode 100644
index 0000000..f3ebd7b
--- /dev/null
+++ b/TinyPOS/TinyPosEntity/Service/TransactionService.cs
@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TinyPosEntity.Entity;
+
+namespace TinyPosEntity.Service
+{
+    public class TransactionService
+    {
+        static TransactionService instance;
+        public static TransactionService Instance { get { Init(); return instance; } }
+
+        private static void Init()
+        {
+            if (instance == null)
+                instance = new TransactionService();
+        }
+
+        public void Create(Transaction targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                context.Transactions.Add(targetObject);
+                context.SaveChanges();
+            }
+        }
+
+        public void Create(List<Transaction> targetObject)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                foreach (Transaction type in targetObject)
+                {
+                    context.Transactions.Add(type);
+                }
+
+                context.SaveChanges();
+            }
+        }
+
+        public List<Transaction> Find(DateTime fromDateTime, DateTime toDateTime)
+        {
+            using (EntityContext context = new EntityContext())
+            {
+                var qry = from t in context.Transactions
+                          where (t.Timestamp >= fromDateTime && t.Timestamp <= toDateTime)
+                          orderby t.Timestamp descending
+                          select t;
+
+                if (qry.Count() < 1)
+                    return null;
+
+                return qry.ToList();
+            }
+        }
+    }
+}