其实很简单:
Dim nms1() As String = {"日期","内容","次数","时间"}
Dim nms2() As String = {"前座_左","前座_右","后座_左","后座_右"}
DataTables("表B").DataRows.Clear()
For Each dr1 As DataRow In DataTables("表A").DataRows
For Each nm2 As String In nms2
If dr1.IsNull(nm2 & "_姓名") = False
Dim dr2 As DataRow = DataTables("表B").AddNew
dr2("姓名") = dr1(nm2 & "_姓名")
dr2("类型") = dr1(nm2 & "_科目")
For Each nm1 As String In nms1
dr2(nm1) = dr1(nm1)
Next
End If
Next
Next