如何将对象从 IEnumerable 集合添加到数据库？

Question

我有一个 ienumerable 实体的集合要添加到数据库中，但似乎需要进行一些转换。谁能指出我正确的方向？

bool InsertDetails(DataTable detailTable, string fileName)
{
    using (SunseapEBTContext context = new SunseapEBTContext())
    {
        if (InsertMaster(fileName))//if creating master record successful
        {                    
            int masterId = GetSPReadingM(m => m.FileName == fileName).SPReadingMasterId; //get MasterID of file uploaded

             var details = detailTable.AsEnumerable().Select(row => new LeasingSPReadingDetailEntity()//new entity from datatable
             {
                //SPReadingId = row.Field<long>("ProductID"),

                        SPReadingMasterId = masterId,
                        BillCycleYear = int.Parse(row.Field<int>("Bill Cycle").ToString().Substring(0, 4)),
                        BillCycleMonth = byte.Parse(row.Field<byte>("Bill Cycle").ToString().Substring(4))

            });
            foreach(IEnumerable<LeasingSPReadingDetailEntity> detail  in details)
            {                       
                context.LeasingSPReadingDetailEntities.AddObject(detail);
            }
            context.SaveChanges();                    
        }
        return true;
    }
}

在foreach循环中，抛出异常

CS1503 Argument 1: cannot convert from 'System.Collections.Generic.IEnumerable' to 'SunseapEBT.Domain.BillingModule.LeasingContract.Entity.LeasingSPReadingDetailEntity'

LeasingSPReadingDetailEntity class:

public class LeasingSPReadingDetailEntity
{
    public long SPReadingId { get; set; }
    public int SPReadingMasterId { get; set; }
    public int BillCycleYear { get; set; }
    public byte BillCycleMonth { get; set; }

}

更多信息：包含详细信息的文件已上传，将在一个 table 中创建一个主记录。文件中的详细信息将添加到单独的 table 中，其中自动生成的 masterId 来自第一个 table。问题是无法将详细信息添加到数据库中。

编辑：我发现了为什么会出现错误。错误是因为文件的内容。有些行没有输入值，最后一行不遵循其余行的格式，因为它显示了总行数。感谢大家的帮助！

Answer 1

将其更改为列表，然后添加项目。

var details = detailTable.AsEnumerable().Select(row => new  LeasingSPReadingDetailEntity()//new entity from datatable
         {
            SPReadingId = row.Field<long>("ProductID"),
            SPReadingMasterId = masterId,
            BillCycleYear = int.Parse(row.Field<int>("Bill Cycle").ToString().Substring(0, 4)),
            BillCycleMonth = byte.Parse(row.Field<byte>("Bill Cycle").ToString().Substring(4)),
        }).ToList();
        foreach(var detail  in details)
        {                       
            context.LeasingSPReadingDetailEntities.Add(detail);
        }

或更好：

var details = detailTable.AsEnumerable().Select(row => new  LeasingSPReadingDetailEntity()//new entity from datatable
         {
            SPReadingId = row.Field<long>("ProductID"),
            SPReadingMasterId = masterId,
            BillCycleYear = int.Parse(row.Field<int>("Bill Cycle").ToString().Substring(0, 4)),
            BillCycleMonth = byte.Parse(row.Field<byte>("Bill Cycle").ToString().Substring(4)),
        }).ToList();

context.LeasingSPReadingDetailEntities.AddRange(details);

Answer 2

您可以将有问题的 foreach 循环更改为以下任一循环。我更喜欢第一个，因为它不那么冗长。

            foreach(var detail  in details)
            {                       
                context.LeasingSPReadingDetailEntities.AddObject(detail);
            }

或

            foreach(LeasingSPReadingDetailEntity detail  in details)
            {                       
                context.LeasingSPReadingDetailEntities.AddObject(detail);
            }

如果您查看 foreach 循环的语法，第一个构造 variableType 是存储在集合中的元素的类型（在您的情况下为 LeasingSPReadingDetailEntity ）而不是集合的类型。你做了后者，这就是你得到无效转换错误的原因。

foreach(variableType currentElementBeingIterated in collection){

    //code block to operate on currentElement

  }

Answer 3

@slawekwin 评论就是答案。但我认为有更好的解决方案，因为您的代码似乎迭代了 2 次：第一次生成新的 Enumerable（浪费内存），第二次将对象添加到上下文中。

不妨在迭代每一行时直接添加对象。

foreach(var row in detailTable.AsEnumerable())
{                       
    context.LeasingSPReadingDetailEntities.AddObject(
        new LeasingSPReadingDetailEntity()//new entity from datatable
        {
           //SPReadingId = row.Field<long>("ProductID"),

           SPReadingMasterId = masterId,
           BillCycleYear = int.Parse(row.Field<string>("Bill Cycle").Substring(0, 4)),
           BillCycleMonth = byte.Parse(row.Field<string>("Bill Cycle").Substring(4)),
           AccountNumber = row.Field<string>("Account No."),
           PeriodStart = row.Field<DateTime>("Period Start"),
           PeriodEnd = row.Field<DateTime>("Period End"),
           TownCouncil = row.Field<string>("Customer Name"),
           Service = row.Field<string>("Service Type"),
           Adjustment = row.Field<string>("Adjustment"),
           Block = row.Field<string>("Blk"),
           AddressLine1 = row.Field<string>("Adress Line 1"),
           AddressLine2 = row.Field<string>("Adress Line 2"),
           AddressLine3 = row.Field<string>("Postal Code"),
           Usage = row.Field<decimal>("Usage"),
           Rate = row.Field<decimal>("Rate"),
           Amount = row.Field<decimal>("Amount")
        }
    );
}

--- 编辑 ---

我不确定，但我可以猜到 "Bill Cycle" 字段既不是 int 也不是 byte。因此，您应该将其作为字符串检索，然后将其解析为您的新对象。这是我更改的部分：

BillCycleYear = int.Parse(row.Field<string>("Bill Cycle").Substring(0, 4)),
BillCycleMonth = byte.Parse(row.Field<string>("Bill Cycle").Substring(4)),

如何将对象从 IEnumerable 集合添加到数据库？

How to add object to database from an IEnumerable collection?

c#

database

ienumerable

entity-framework