SITE-50: Fixing rounding problems (#289)

* Fixing rounding problems

* Refactoring rounding solution

* Simplifying code

src/Libraries/OrchardCore.Commerce.MoneyDataType/Amount.cs

@@ -61,8 +61,7 @@ public Amount(decimal value, CultureInfo? culture)
     public Amount(decimal value, ICurrency? currency)
     {
         _currency = currency ?? MoneyDataType.Currency.UnspecifiedCurrency;
-        // The value is rounded to avoid storing more precision than what the currency supports.
-        Value = Math.Round(value, _currency.DecimalPlaces);
+        Value = value;
     }
 
     public bool Equals(Amount other) =>
@@ -81,6 +80,9 @@ public int CompareTo(Amount other)
         return Value.CompareTo(other.Value);
     }
 
+    public Amount GetRounded() =>
+        new(Math.Round(Value, Currency.DecimalPlaces), Currency);
+
     private void ThrowIfCurrencyDoesntMatch(Amount other, string operation = "compare")
     {
         if (Currency.Equals(other.Currency)) return;

src/Libraries/OrchardCore.Commerce.MoneyDataType/Extensions/EnumerableExtensions.cs

@@ -1,4 +1,4 @@
-using OrchardCore.Commerce.MoneyDataType.Abstractions;
+using OrchardCore.Commerce.MoneyDataType.Abstractions;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -33,4 +33,7 @@ public static Amount Sum(this IEnumerable<Amount> amounts)
 
         return currency == null ? Amount.Unspecified : new Amount(sum, currency);
     }
+
+    public static IEnumerable<Amount> Round(this IEnumerable<Amount> amounts) =>
+        amounts.Select(amount => amount.GetRounded());
 }

src/Modules/OrchardCore.Commerce/Services/ShoppingCartHelpers.cs

@@ -6,6 +6,7 @@
 using OrchardCore.Commerce.Extensions;
 using OrchardCore.Commerce.Models;
 using OrchardCore.Commerce.MoneyDataType;
+using OrchardCore.Commerce.MoneyDataType.Extensions;
 using OrchardCore.Commerce.ViewModels;
 using System.Collections.Generic;
 using System.Linq;
@@ -94,7 +95,14 @@ private async Task<ShoppingCartViewModel> CreateShoppingCartViewModelAsync(
             totals = lines.CalculateTotals().ToList();
         }
 
-        model.Totals.AddRange(totals);
+        // The values are rounded to avoid storing more precision than what the currency supports.
+        foreach (var line in lines)
+        {
+            line.LinePrice = line.LinePrice.GetRounded();
+            line.UnitPrice = line.UnitPrice.GetRounded();
+        }
+
+        model.Totals.AddRange(totals.Round());
         model.Headers.AddRange(headers);
         model.Lines.AddRange(lines);