IEnumerable <T>用匿名方法

Question

我不知道如何擺脫這個錯誤？

錯誤1使用泛型類型'System.Collections.Generic.IEnumerable'需要1個類型參數C：\ Users \ huzaifa.gain \ documents \ visual studio 2010 \ Projects \ VendInvoiceImport \ VendInvoiceImport \ Program.cs 34 24 VendInvoiceImport

private static IEnumerable<string , string > DistinctInvoiceNumber(DataTable VendorInvoiceStagingTable) 
     { 
      var InvoiceLinecollection = VendorInvoiceStagingTable.AsEnumerable().Select(t => new { number = t.Field<string>(VendInvoice.Number),LineNumber = t.Field<string>(VendInvoice.LineNumber)}).Distinct(); 
     return InvoiceLinecollection; 
     } 

Answer 1

您的Linq查詢返回一個匿名類型的序列，但方法不能返回匿名類型。您有幾種選擇：

• 返回IEnumerable<Tuple<string, string>>

  private static IEnumerable<Tuple<string, string>> DistinctInvoiceNumber(DataTable VendorInvoiceStagingTable) 
  { 
      var InvoiceLinecollection = VendorInvoiceStagingTable 
              .AsEnumerable() 
              .Select(t => Tuple.Create(t.Field<string>(VendInvoice.Number), t.Field<string>(VendInvoice.LineNumber))) 
              .Distinct(); 
      return InvoiceLinecollection; 
  } 
  

• 回報作爲另一個答案建議（假設你的查詢不返回重複鍵）

  private static IDictionary<string, string> DistinctInvoiceNumber(DataTable VendorInvoiceStagingTable) 
  { 
      var InvoiceLinecollection = VendorInvoiceStagingTable 
              .AsEnumerable() 
              .Select(t => Tuple.Create(t.Field<string>(VendInvoice.Number), t.Field<string>(VendInvoice.LineNumber))) 
              .Distinct() 
              .ToDictionary(t => t.Item1, t => t.Item2); 
      return InvoiceLinecollection; 
  } 
  

• 一個IDictionary<string, string>用2個字符串屬性爲此創建一個類並返回該類的序列

  private static IEnumerable<InvoiceLine> DistinctInvoiceNumber(DataTable VendorInvoiceStagingTable) 
  { 
      var InvoiceLinecollection = VendorInvoiceStagingTable 
              .AsEnumerable() 
              .Select(t => new InvoiceLine(t.Field<string>(VendInvoice.Number), t.Field<string>(VendInvoice.LineNumber))) 
              .Distinct(); 
      return InvoiceLinecollection; 
  } 
  

Answer 2

爲什麼你不使用Dictionary<string, string>呢？

private static Dictionary<string , string > DistinctInvoiceNumber(DataTable VendorInvoiceStagingTable) 
     { 
      var InvoiceLinecollection = VendorInvoiceStagingTable.AsEnumerable().Select(t => new { number = t.Field<string>(VendInvoice.Number),LineNumber = 
       t.Field<string>(VendInvoice.LineNumber)}).ToDictionary(); 
      return InvoiceLinecollection; 
      }