我正在从以下VB.NET代码这个例外只有某些月份:转换无效
System.InvalidCastException: Conversion from type 'DBNull' to type 'Date' is not valid.
它发生就行了:
If CDate(dRow("CompleteDate")).ToString("d") = arrWeekYear(i, 1).ToString("d") Then
如果我正确理解这个问题,那么问题是我想比较一些NULL的值为一个非NULL值的CompleteDate。
我该如何解决这个问题?对于某些日期,上面的代码完美运行。但是对于一些更新的记录,事实并非如此。但是我能够从具有相同日期范围的T-SQL查询中获得输出,并且没有错误;它也很快运行。我检查了这个“Date_Completed”和“Review_Date”NULL值的T-SQL查询,但无论如何,“CompleteDate”总是= NON-Null值。所以我不明白这是怎么发生的。
这里是我的VB.NET查询:
commandstring = "SELECT Batch_Records.Part_Number, Batch_Records.Lot_Number, Batch_Records.Date_Received, " & _
"IsNull([Date_Completed], [Review_Date]) AS [CompleteDate], Batch_Records.Error, " & _
"Batch_Records.[Group], Batch_Records.MFG, Batch_Records.MFG2, Batch_Records.QC, Batch_Records.QC2, " & _
"QC_CODES.CODE_DESC, DATEADD(DD, 1 - DATEPART(DW, Batch_Records.Date_Received), Batch_Records.Date_Received) AS SundayDate " & _
"FROM EXCEL.Batch_Records LEFT JOIN EXCEL.QC_CODES ON Batch_Records.Part_Number = QC_CODES.CODE_ID " & _
"WHERE (Batch_Records.[Group]" & TheGroup & " AND Batch_Records.Date_Received > '" & FirstWeek & "' AND Batch_Records.Date_Received < dateadd(Day, 1, '" & LastWeek & "'))" & _
"ORDER BY Batch_Records.Date_Received"
当我添加了导致错误的线高于此线以上,我的报告超时这些个月。那么该怎么办?
If Not dRow("CompleteDate") Is System.DBNull.Value Then
NOOOO!不要使用字符串连接来将值替换为查询! **不要这样做!** –
他是对的,有了这段代码,你可以很容易地注入sql! – David
在您的查询中,是“EXCEL”模式,还是您以某种方式加入Excel表单?或者我们只处理SQL? –