计算代码执行耗时

Dim st As Date = Date.Now
'要测试耗时的代码
MessageBox.Show("耗时: " & (Date.Now - st).TotalSeconds & "秒")

例如：

Dim st As Date = Date.Now '将开始时间保存在变量st中
Dim nms As List(of String) = DataTables("表A").GetValues("客户")
DataTables("表B").StopRedraw()
For Each nm As String In nms
    Dim dr As DataRow = DataTables("表B").AddNew()
    dr("客户") = nm
    dr("付款合计") = DataTables("表A").Compute("Sum(金额)", "客户 = '" & nm & "' And tk = 1")
    dr("欠款合计") = DataTables("表A").Compute("Sum(金额)", "客户 = '" & nm & "' And tk = 0")
Next
DataTables("表B").ResumeRedraw()
MessageBox.Show("耗时: " & (Date.Now - st).TotalSeconds & "秒") '计算并显示执行代码所花费的秒数