無法轉換的源類型System.Nullable <double>

Question

這裏是我的腳本：

public PlainBrgDataSummaryComplete SummaryComputationPerTransSQLite(long ProgramID) 
{ 
    PlainBrgDataSummaryComplete result = new PlainBrgDataSummaryComplete(); 
    DataSet dataSet = GetPlainBrgDataSQLite(ProgramID); 

    var abcde = dataSet.Tables["dataBridge"] 
     .AsEnumerable() 
     //.Where(a => Convert.ToDateTime(a["reportingDate"].ToString()) >= startOfWeek1 && Convert.ToDateTime(a["reportingDate"].ToString()) < endOfWeek1.AddDays(1)) 
     .GroupBy(a => 1) 
     .Select(d => 
      new PlainBrgDataSummaryTrans 
      { 
       transactionWk6 = d.Sum(a => a.Field<double?>("TranCount")) 

      } 
     ).FirstOrDefault(); 

    result.totaltransaction = new PlainBrgDataSummaryTrans 
    { 
     transactionWk6 = abcde; 
    }; 

    return result; 
} 

我得到的錯誤 - 不能源類型轉換爲System.Nullable<double>。具體在transactionWk6 = abcde部分;

Answer 1

abcde已經是一個PlainBrgDataSummaryTrans類型，因爲你是投影select聲明它。

嘗試使用這樣的：

result.totaltransaction = abcde; 
return result; 

Answer 2

米哈伊爾Stancescu應該解決的問題。但考慮到你的返回類型，你不需要額外的任務。你可以像修改代碼如下

public PlainBrgDataSummaryComplete SummaryComputationPerTransSQLite(long ProgramID) 
{ 
DataSet dataSet = GetPlainBrgDataSQLite(ProgramID); 

return dataSet.Tables["dataBridge"] 
    .AsEnumerable() 
    //.Where(a => Convert.ToDateTime(a["reportingDate"].ToString()) >= startOfWeek1 && Convert.ToDateTime(a["reportingDate"].ToString()) < endOfWeek1.AddDays(1)) 
    .GroupBy(a => 1) 
    .Select(d => 
     new PlainBrgDataSummaryTrans 
     { 
      transactionWk6 = d.Sum(a => a.Field<double?>("TranCount")) 

     } 
    ).FirstOrDefault(); 

}