Question

我正在尝试学习/制作MVC 5电子商务Web应用程序。除了购买物品外，所有东西都可以正常工作。该项目在数据库中重复，而不是减去所购买产品的数量。我应该如何更改我的代码来做到这一点？

我尝试了多种将商品ID与订单商品ID关联的方法，但是却出现了错误。任何帮助，将不胜感激。谢谢。

 public string GetSelectStatement(string JsonDataForSelect)
    {
        var root = (JObject)JsonConvert.DeserializeObject(JsonDataForSelect);
        var query = "";
        var query1 = "";
        var query2 = "";
        string[] tableName = new string[] { };
        var items = root.SelectToken("Details").Children().OfType<JProperty>().ToDictionary(p => p.Name, p => p.Value);
        foreach (var item in items)
        {
            if (item.Key == "table")
            {
                tableName = JsonConvert.DeserializeObject<string[]>(item.Value.ToString());
            }
            else if (item.Key == "fields")
            {
                var key = item.Value.SelectToken("").OfType<JProperty>().ToDictionary(p => p.Name, p => p.Value);
                var count = 0;
                foreach (var id in key)
                {
                    count++;
                    if (count == key.Count())
                    {
                        query1 += string.Format("{0}.{1}", tableName[1], id.Key);
                    }
                    else
                    {
                        query1 += string.Format("{0}.{1},", tableName[1], id.Key);
                    }
                    query = string.Format("select {0} from {1} inner join {2} on {3} where ", query1, tableName[0], tableName[1], query2);
                }
            }
            else if (item.Key == "keys")
            {
                var key = item.Value.SelectToken("").OfType<JProperty>().ToDictionary(p => p.Name, p => p.Value);
                var count = 0;
                if (query2 == "")
                {
                    foreach (var id in key)
                    {
                        count++;
                        if (count == key.Count())
                        {
                            query2 += string.Format("{0}.{1}={2}.{3}", tableName[0], id.Key, tableName[1], id.Key);
                        }
                        else
                        {
                            query2 += string.Format("{0}.{1}={2}.{3},", tableName[0], id.Key, tableName[1], id.Key);
                        }
                        query = string.Format("select {0} from {1} inner join {2} on {3} where ", query1, tableName[0], tableName[1], query2);
                    }
                }
                count = 0;
                foreach (var id in key)
                {
                    count++;
                    if (count == key.Count())
                    {
                        query += string.Format("{0}.{1}={2} ", tableName[0], id.Key, id.Value);
                    }
                    else
                    {
                        query += string.Format("{0}.{1}={2} and ", tableName[0], id.Key, id.Value);
                    }
                }
            }
        }
        return query;
    }

Answer 1

您正在通过致电添加购物车中的物品

orderItems.Add（orderItem）

您的上下文会将其视为新项目。您在这里有两个选择：

通过调用_context.Items.Attach(orderItem)
从上下文中重新加载项目，例如通过致电orderItems.Add(_context.Items.Single(x => x.id == orderItem.Id)

检查Working with entity states以获得详细信息。

签出期间在数据库中记录重复

1 个答案: