主题：[求助]计算每年的出差天数（起止日期跨年）

做一个按钮，执行代码

Dim dt1 As DataTable = DataTables("年出差天数统计")
Dim dt2 As DataTable = DataTables("出差信息登记表")
dt1.DataRows.Clear
For Each xm As String In dt2.GetValues("姓名")
    Dim ndr As DataRow = dt1.AddNew
    Dim drs = dt2.Select("姓名 = '" & xm & "'")
    For Each dc As DataCol In dt1.DataCols
        If dc.name.StartsWith("年度_") Then
            Dim sum As Double = 0
            For Each dr As DataRow In drs
                Dim d1 As Date = dr("出差起始日期")
                Dim d2 As Date = dr("出差结束日期")
               
                Dim y As Integer = dc.name.Replace("年度_", "")
                If y >= d1.Year AndAlso y <= d2.Year Then
                    If d1.year = d2.year Then
                        sum += (d2-d1).TotalDays
                    ElseIf y = d1.year Then
                        Dim d As Date = new Date(y+1, 1, 1)
                        sum += (d-d1).TotalDays - 1
                    ElseIf y = d2.year Then
                        Dim d As Date = new Date(y, 1, 1)
                        sum += (d2-d).TotalDays + 1
                    Else
                        Dim d As Date = new Date(y, 1, 1)
                        Dim d3 As Date = d.AddYears(1)
                        sum += (d3-d).TotalDays + 1
                    End If
                End If
               
            Next
            ndr(dc.name) = sum
        End If
    Next
    ndr("姓名") = xm
Next