主题：求教：如何实现签退时间减签到时间等于在线时长?

 如下代码，一次性统计

Dim xms As List(Of String) = DataTables("表A").GetValues("姓名")
For Each xm As String In xms
    Dim drs As List(of DataRow) = DataTables("表A").Select("姓名 = '" & xm & "'", "登记时间")
    For i As Integer = 0 To iif(drs.Count Mod 2 = 0, drs.count - 1, drs.count - 2) Step 2
        drs(i)("在线时长") = (drs(i+1)("登记时间") - drs(i)("登记时间")).TotalMinutes
        drs(i+1)("在线时长") = drs(i)("在线时长")
    Next
Next