主题：请看看出现这个错误我该怎么改？

 你判断一下空值不参与运算即可

 If dr.IsNull("上牌日期") = false Then

 2月29日的问题

Dim nmyc As String
For Each dr As DataRow In DataTables("主表").DataRows
    If dr.IsNull("上牌日期") = False Then
        Dim dt2 As Date = dr("上牌日期")
        If dt2.Month = 2 AndAlso dt2.Day = 29 AndAlso Date.IsLeapYear(Date.Today.Year) = False Then
            dt2 = new Date(Date.Today.Year,dt2.Month, 28)
        Else
            dt2 = new Date(Date.Today.Year,dt2.Month,dt2.Day)
        End If
        If dt2 >= Date.Today AndAlso dt2 < Date.Today.AddMonths(1) Then
            nmyc = nmyc & ",'" & dr("_Identify") & "'"
        End If
       
    End If
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