主题：老师，通过for each 集合 去修改这个集合要怎么做？

For Each dr2 As DataRow In drs
            For Each tx As String In txm
                If dr2.lines("药品类别").Contains(tx) = False Then
                    drs.Remove(dr2)
                    Exit For
                End If
            Next
        Next

运行到这段就提示集合已修改。