diff --git a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderAuthorizationTests.cs b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderAuthorizationTests.cs
index 1f72ef936e..4710ef2f4b 100644
--- a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderAuthorizationTests.cs
+++ b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderAuthorizationTests.cs
@@ -46,13 +46,14 @@ public async Task Anonymous_PaymentOrder_Card_Authorization(Product[] products,
                         Is.EqualTo(State.Completed));
 
             // Order Items
+            
             Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.Count, Is.EqualTo(products.Count()));
             for (var i = 0; i < products.Count(); i++)
             {
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Name, Is.EqualTo(products[i].Name));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Quantity, Is.EqualTo(products[i].Quantity));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Name, Is.EqualTo(products[i].Name));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Quantity, Is.EqualTo(products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
             }
         }
 
@@ -92,10 +93,10 @@ public async Task Anonymous_PaymentOrder_Invoice_Authorization(Product[] product
             Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.Count, Is.EqualTo(products.Count()));
             for (var i = 0; i < products.Count(); i++)
             {
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Name, Is.EqualTo(products[i].Name));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Quantity, Is.EqualTo(products[i].Quantity));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Name, Is.EqualTo(products[i].Name));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Quantity, Is.EqualTo(products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
             }
         }
 
diff --git a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderSaleTests.cs b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderSaleTests.cs
index e13efda90a..6f6e61f5e2 100644
--- a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderSaleTests.cs
+++ b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Anonymous/AnonymousPaymentOrderSaleTests.cs
@@ -49,10 +49,10 @@ public async Task Anonymous_PaymentOrder_Swish_Sale(Product[] products, PayexInf
             Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.Count, Is.EqualTo(products.Count()));
             for (var i = 0; i < products.Count(); i++)
             {
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Name, Is.EqualTo(products[i].Name));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Quantity, Is.EqualTo(products[i].Quantity));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Name, Is.EqualTo(products[i].Name));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Quantity, Is.EqualTo(products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
             }
         }
 
diff --git a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderAuthorizationTests.cs b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderAuthorizationTests.cs
index 55d39de2ac..e77058514b 100644
--- a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderAuthorizationTests.cs
+++ b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderAuthorizationTests.cs
@@ -49,10 +49,10 @@ public async Task Standard_PaymentOrder_Card_Authorization(Product[] products, P
             Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.Count, Is.EqualTo(products.Count()));
             for (var i = 0; i < products.Count(); i++)
             {
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Name, Is.EqualTo(products[i].Name));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Quantity, Is.EqualTo(products[i].Quantity));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Name, Is.EqualTo(products[i].Name));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Quantity, Is.EqualTo(products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
             }
         }
 
@@ -92,10 +92,10 @@ public async Task Standard_PaymentOrder_Invoice_Authorization(Product[] products
             Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.Count, Is.EqualTo(products.Count()));
             for (var i = 0; i < products.Count(); i++)
             {
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Name, Is.EqualTo(products[i].Name));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Quantity, Is.EqualTo(products[i].Quantity));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Name, Is.EqualTo(products[i].Name));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Quantity, Is.EqualTo(products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
             }
         }
 
diff --git a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderSaleTests.cs b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderSaleTests.cs
index 40eb81e726..371b1565b1 100644
--- a/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderSaleTests.cs
+++ b/src/Samples/Sample.AspNetCore.SystemTests/Test/PaymentTests/PaymentOrder/Standard/StandardPaymentOrderSaleTests.cs
@@ -49,10 +49,10 @@ public async Task Standard_PaymentOrder_Swish_Sale(Product[] products, PayexInfo
             Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.Count, Is.EqualTo(products.Count()));
             for (var i = 0; i < products.Count(); i++)
             {
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Name, Is.EqualTo(products[i].Name));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Quantity, Is.EqualTo(products[i].Quantity));
-                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList[i].Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Name, Is.EqualTo(products[i].Name));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).UnitPrice.Value, Is.EqualTo(products[i].UnitPrice));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Quantity, Is.EqualTo(products[i].Quantity));
+                Assert.That(order.PaymentOrderResponse.OrderItems.OrderItemList.ElementAt(i).Amount.Value, Is.EqualTo(products[i].UnitPrice * products[i].Quantity));
             }
         }
 
diff --git a/src/SwedbankPay.Sdk/PaymentOrders/OrderItems.cs b/src/SwedbankPay.Sdk/PaymentOrders/OrderItems.cs
index 5f44b75206..d9be93111f 100644
--- a/src/SwedbankPay.Sdk/PaymentOrders/OrderItems.cs
+++ b/src/SwedbankPay.Sdk/PaymentOrders/OrderItems.cs
@@ -4,12 +4,16 @@ namespace SwedbankPay.Sdk.PaymentOrders
 {
     public class OrderItems : IdLink
     {
+        public OrderItems(IEnumerable<OrderItem> orderItemList)
+        {
+            OrderItemList = orderItemList;
+        }
         /// <summary>
         ///     The orderItems property of the paymentOrder is an array containing the items being purchased with the order. Used
         ///     to print on invoices if
         ///     the payer chooses to pay with invoice, among other things. Order items can be specified on both payment order
         ///     creation as well as on Capture.
         /// </summary>
-        public List<OrderItem> OrderItemList { get; set; }
+        public IEnumerable<OrderItem> OrderItemList { get; set; }
     }
 }
\ No newline at end of file
diff --git a/src/SwedbankPay.Sdk/PaymentOrders/PaymentOrderResource.cs b/src/SwedbankPay.Sdk/PaymentOrders/PaymentOrderResource.cs
index 4905fd5240..ad2cf8d696 100644
--- a/src/SwedbankPay.Sdk/PaymentOrders/PaymentOrderResource.cs
+++ b/src/SwedbankPay.Sdk/PaymentOrders/PaymentOrderResource.cs
@@ -1,6 +1,9 @@
 using System;
+using System.Net.Http;
 using System.Threading.Tasks;
 
+using SwedbankPay.Sdk.Exceptions;
+
 namespace SwedbankPay.Sdk.PaymentOrders
 {
     internal class PaymentOrderResource : ResourceBase, IPaymentOrderResource
@@ -29,6 +32,10 @@ public async Task<PaymentOrder> Create(PaymentOrderRequest paymentOrderRequest,
         /// <param name="id"></param>
         /// <param name="paymentOrderExpand"></param>
         /// <returns></returns>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <exception cref="InvalidOperationException"></exception>
+        /// <exception cref="HttpRequestException"></exception>
+        /// <exception cref="HttpResponseException"></exception>
         public Task<PaymentOrder> Get(Uri id, PaymentOrderExpand paymentOrderExpand = PaymentOrderExpand.None)
         {
             if (id == null)