elapsed.Milliseconds 获取毫秒。
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每100毫秒，do中的代码执行一次，执行时间将大于100毫秒，这是产生误差的地方之一。invoke执行一个方法txt，必须等txt里面的代码运行完毕，方法才能返回，期间占用的时间全是“误差”。
无限循环，且没有退出机制，停不下来。
format是肯定不能带毫秒滴。要实现你的效果，也简单
Format(time,"YYYY-MM-DD HH:MM:SS") "." ( timer()*1000 mod 1000)
Format(time,"YYYY-MM-DD HH:MM:SS") 加上 . 再加上毫秒数，就构成了
timer()代表的是，从午夜到现在，所经过的秒数，它的小数部分x1000就是毫秒
试过NN次后，我“也”发现这种记录时间的精度为10.0144毫秒，
看来，这个问题是由CLR决定的，如果，只使用FCL的函数，看来没办法解决这一问题了！
看了 LoveCherry(论成败，人生豪迈；大不了，重头再来！^_^) ，给出的文章链接，
受了些启发，对于文章中实现的那个A类，我没看太明白，但是，文章中用到了QueryPerformanceCounterp这个win API函数，楼主，可以导入用一下，我试过多次，在我的机子上，其精度为 210/1000 毫秒左右。
QueryPerformanceCounter这个函数的是一个计数器函数，以百万分之一秒为单位，来记算时间数。
//=============
using System.Runtime.InteropServices;
using System.Threading;
[DllImport("kernel32.dll")]
static extern bool QueryPerformanceCounter([In, Out] ref long lpPerformanceCount);
long t1 = 0;
long t2 = 0;
QueryPerformanceCounter(ref t1);
Thread.Sleep(1); //挂起一毫秒，作为演示
QueryPerformanceCounter(ref t2);
long sp = t2 - t1;//sp的单位为百万分之一秒
float f_time = (float)((decimal) sec / (decimal)10000); //得到0.0001毫秒的精度
f_time = float.Parse(string.Format("{0:F1}",f_time)); //f_time是经过四舍五入，得到的0.1毫秒的精度
不需要控件就可以，用多线程的方式实现，在窗体上放一个Label和一个button按钮，代码如下：
Imports System.Threading
Public Class Form1
Dim Start As Double
Dim td As Thread
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Label1.Text = "00:00:00 000"
Button1.Text = "开始"
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If Button1.Text = "开始" Then
Button1.Text = "结束"
Start = DateAndTime.Timer
td = New Thread(AddressOf fun1)
td.Start()
Else
Button1.Text = "开始"
td.Abort()
End If
End Sub
'定义一个线程
Private Sub fun1()
Dim elapsed As TimeSpan
Dim Dg_txt As New Dg(AddressOf txt)
Do
elapsed = TimeSpan.FromMilliseconds((DateAndTime.Timer - Start) * 1000)
Me.Invoke(Dg_txt, elapsed.ToString, Label1)
Thread.Sleep(100)
Loop
End Sub
'定义一个委托
Delegate Sub Dg(ByVal s As String, ByVal obj As Label)
Sub txt(ByVal s As String, ByVal obj As Label)
obj.Text = s
End Sub
End Class
dim a1 as timespan = dtEndTime -dtStartTime
dim a2 as integer = a1.TotalMilliseconds
是我以前自己设计的用来测试自己点钞速度用的，希望是你需要的
以下是窗体的全部代码
Public Class Form1
Dim StartFlag As Boolean = False
Dim secon As Integer
Dim minut As Integer
'空格
Private Sub Form1_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyUp
If e.KeyCode = Keys.Space Then
If StartFlag Then
StartFlag = False
Timer1.Enabled = False
If Val(Strings.Right(Label1.Text, 2)) 10 And Val(Strings.Right(Label1.Text, 2)) = 0 Then secon = 0 : minut = 0 : Label1.Text = "00:00" : Exit Sub
ListBox1.Items.Add(Label1.Text.ToString)
ListBox1.SelectedItem = ListBox1.Items.Count - 1
Label1.Focus()
Button1.Enabled = True
Label1.Text = "00:00"
secon = 0
minut = 0
Else
StartFlag = True
Timer1.Enabled = True
End If
End If
End Sub
'加载
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
ListBox1.Items.Clear()
Label1.Text = "00:00"
Button1.Enabled = False
secon = 0
minut = 0
Label1.Focus()
End Sub
'清空
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Button1.Enabled = False
ListBox1.Items.Clear()
Label1.Focus()
End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
secon += 1
If secon = 60 Then
secon = 0
minut += 1
End If
Dim seconStr As String = secon
If seconStr.Length = 1 Then seconStr = "0" + seconStr
Dim minutStr As String = minut
If minutStr.Length = 1 Then minutStr = "0" + minutStr
Label1.Text = minutStr + ":" + seconStr
Label1.Focus()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim SeconSun As Integer
If ListBox1.Items.Count 0 Then
For i = 0 To ListBox1.Items.Count - 1
Dim TemStr As String = ListBox1.Items.Item(i).ToString
Dim TemInt1 As Integer = Val(Strings.Right(TemStr, 2))
Dim TemInt2 As Integer = Val(Strings.Left(TemStr, 2))
Debug.Print(TemInt1.ToString)
Debug.Print(TemInt2.ToString)
SeconSun += TemInt1 + TemInt2 * 60
Debug.Print(SeconSun.ToString)
Next
TextBox1.Text = (SeconSun / ListBox1.Items.Count).ToString + "秒"
End If
Label1.Focus()
End Sub
End Class
