如何從IEnumerable集合中添加對象到數據庫？

Question

我有一個可枚舉實體集合被添加到數據庫，但它似乎需要一些轉換。任何人都可以將我指向正確的方向嗎？

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循環，會引發異常

CS1503參數1：無法從 'System.Collections.Generic.IEnumerable' 轉換爲「SunseapEBT.Domain.BillingModule.LeasingContract.Entity.LeasingSPReadingDetailEntity 「

LeasingSPReadingDetailEntity類：

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： 上傳包含詳細信息的文件，並將在一個表中創建主記錄。文件中的細節將被添加到一個單獨的表中，第一個表中自動生成masterId。該問題無法將詳細信息添加到數據庫中。

編輯： 我發現了爲什麼出現錯誤。該錯誤是由於該文件的內容。有些行沒有輸入值，最後一行沒有遵循其餘行的格式，因爲它顯示了總行數。感謝所有的幫助！

Answer 1

@slawekwin評論是答案。但我認爲有一個更好的解決方案，因爲它看起來像你的代碼迭代2x：1st來生成新的Enumerable（浪費內存），第二個將對象添加到上下文。

不妨直接在迭代每一行時添加對象。

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") 
     } 
    ); 
} 

---編輯---

我不知道，但我可以猜測，「賬期」字段既不是INT也不字節。因此，您應該將其作爲字符串檢索，然後將其解析爲新對象。這是我改變的部分：

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

Answer 2

將其更改爲列表，然後添加該項目。

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); 
     } 

或者更好的是：

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 3

您可以將問題foreach循環更改爲以下的人的。我更喜歡第一個，因爲它不那麼冗長。

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

OR

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

如果你看一下foreach循環的語法，第一個構建variableType是（你的情況LeasingSPReadingDetailEntity）被存儲在集合中的元素的類型，而不是類型的集合。你做了後來的這就是爲什麼你得到無效的轉換錯誤。

foreach(variableType currentElementBeingIterated in collection){ 

    //code block to operate on currentElement 

    }