如何破坏包含三个列表的 List 元素，以便我可以创建一个列表以添加到数据库答案

【问题标题】：How to destruct a List element that contains three lists, so I can create a list to add to database如何破坏包含三个列表的 List 元素，以便我可以创建一个列表以添加到数据库
【发布时间】：2018-03-05 06:46:14
【问题描述】：

进入 webAPI 的是这个 JSON 字符串，并被反序列化为：

List<AddAssignMealView> mealtraiDeserializeObjects = JsonConvert.DeserializeObject<List<AddAssignMealView>>(mealTrainee);

mealtraiDeserializeObjects 包含一周中每一天的五个索引之一。在该特定索引内部是一个如下所示的类：

public class AddAssignMealView
{
    public int TraineeID { get; set; }
    public string DayOfTheWeek { get; set; }
    public List<string> MealTypes { get; set; }
    public List<int> MealID { get; set; }
    public List<string> MealName { get; set; }
}

我想做的是，能够创建MealTrainee(Entity Framework) 的列表：

 public partial class MealTrainee
{
    public int MealTraineeID { get; set; } //Ignore this one due to it being a post
    public int MealID { get; set; }
    public int TraineeID { get; set; }
    public string DayOfTheWeek { get; set; }
    public string MealType { get; set; }
    public string MealName { get; set; }

    public virtual Meal Meal { get; set; }
}

所以我可以使用 addrange 并将列表添加到数据库中。如果它是单个元素，我了解如何使用 zip 并将两种列表类型组合在一起。这是不同的，因为它是一个包含五个元素的列表，而这五个元素中的每一个都包含三个列表。如果有人能指出我正确的方向，那将很有帮助。

【问题讨论】：

AddAssignMealView 的 MealTypes、MealID 和 MealName 列表包含相同的计数？

标签： c# asp.net entity-framework asp.net-web-api

【解决方案1】：

您可以Zip 2 次将 3 个列表中的值组合成一系列元组。您可以使用SelectMany 来展平结果。例如：

var result = mealtraiDeserializeObjects.SelectMany(c =>
    c.MealID.Zip(c.MealName, (id,name) => new {id, name})
    .Zip(c.MealTypes, (prev, type) => new {prev.id, prev.name, type})
    .Select(r => new MealTrainee
    {
        TraineeID = c.TraineeID,
        DayOfTheWeek = c.DayOfTheWeek,
        MealID = r.id,
        MealName = r.name,
        MealType = r.type,
    }));

【讨论】：

【解决方案2】：

这是我找到的解决方案。我每天都在第一次迭代是星期一，然后是用餐次数（例如：早餐用餐，午餐用餐）并将它们计入“用餐周”的计数中。然后我参加了mealweek，并为每个计数创建了一个新的mealtrainee。然后，在我用 mealtrainee 做饭后，我把它放在 db.MealTrainees.AddRange 中并发布了所有记录。

    [ResponseType(typeof(MealTrainee))]
    public IHttpActionResult PostMealTrainee([FromBody] string mealTrainee)
    {
        List<MealTrainee> meals = new List<MealTrainee>();

        using (DbContextTransaction dbContextTransaction = db.Database.BeginTransaction())
        {
            try
            {
                List<AddAssignMealView> mealtraiDeserializeObjects = JsonConvert.DeserializeObject<List<AddAssignMealView>>(mealTrainee);

                foreach (var mealtraiDeserializeObject in mealtraiDeserializeObjects)
                {
                    var mealWeek = mealtraiDeserializeObject.MealID.Select((m, i) => new
                    {
                        mealtraiDeserializeObject.TraineeID,
                        mealtraiDeserializeObject.DayOfTheWeek,
                        MealID = m,
                        MealTypes = mealtraiDeserializeObject.MealName[i],
                        MealName = mealtraiDeserializeObject.MealTypes[i]
                    }).ToList();

                 var meal = mealWeek.Select(x => new MealTrainee()
                    {
                        DayOfTheWeek = x.DayOfTheWeek,
                        MealID = x.MealID,
                        MealName = x.MealName,
                        MealType = x.MealTypes,
                        TraineeID = x.TraineeID
                    }).ToList();

                    db.MealTrainees.AddRange(meal);
                }

                if (!ModelState.IsValid)
                {
                    return BadRequest(ModelState);
                }

                db.SaveChanges();
                dbContextTransaction.Commit();
                return Ok(meals);
            }
            catch (Exception e)
            {
                dbContextTransaction.Rollback();
                Logger.Log(e);
                return BadRequest();
            }
        }
    }

【讨论】：