加快非现有网络股File.Exists [英] Speed up File.Exists for non existing network shares
问题描述
我要检查如果一组文件路径重新present现有文件。
它的工作原理，当路径包含一台机器，这不是目前网络上的网络共享，除了罚款。在这种情况下，它需要一个pretty长的时间（30或60秒）超时。
问题
-
有没有办法缩短非现有网络股超时？ （我敢肯定，当它们确实存在，他们会快速回答，所以1秒的超时将被罚款）
-
是否有任何其他方式来解决这个问题，而无需启动缓存，使算法更复杂？ （也就是说，我已经知道这些X网络共享不存在，跳过匹配的路径的其余部分）
更新：使用线程工作，不是特别优雅，但
公共BOOL pathExists（字符串路径）
{
布尔存在= TRUE;
线程t =新主题
（
新的ThreadStart（委托（）
{
存在= System.IO.File.Exists（路径）;
}）
）;
t.Start（）;
布尔完成= t.Join（500）; //半超时的秒
如果（！完成）{存在= FALSE; t.Abort（）; }
返回的存在;
}
该解决方案避免了每尝试一个线程，首先检查该驱动器可访问和存储的地方。
<一href=\"http://www.experts-exchange.com/Programming/Languages/.NET/Visual_Basic.NET/Q_22595703.html\">Experts交换解决方案 ：
首先，有一个超时的价值，你可以在IsDriveReady功能设置。我有它设置为5秒，但将其设置为你的作品无论
3方法如下使用：
- 首先是得到了WNetGetConnection API函数
UNC（\\服务器名\\共享）驱动器
- 第二个是我们的主要方法：Button1_Click事件
- 第三个是IsDriveReady函数坪服务器。
这工作对我来说太棒了！在这里你去：
'这个API函数将被用于获取驱动器的UNC
私人声明函数库WNetGetConnectionMPR.DLL别名_
WNetGetConnectionA_
（BYVAL lpszLocalName作为字符串_
BYVAL lpszRemoteName作为字符串_
为ByRef cbRemoteName作为Int32）已作为的Int32
这只是一个按钮单击事件 - 加code你相应的事件
私人小组的button1_Click（BYVAL发件人为System.Object的，BYVAL E上System.EventArgs）把手Button1.Click 昏暗bIsReady由于布尔= FALSE 对于每个DRI作为IO.DriveInfo在IO.DriveInfo.GetDrives（） 如果驱动器是一个网络驱动器只，然后ping到它，看它是否已经准备好。
如果dri.DriveType = IO.DriveType.Network然后 获取的该UNC（\\\\服务器\\共享）
通过dri.Name返回驱动器盘符
昏暗UNC作为字符串=空间（100）
WNetGetConnection（dri.Name.Substring（0，2），UNC 100） 'presuming的驱动器映射\\\\服务器\\共享
解析服务器名出的UNC
昏暗的服务器作为字符串= _
。UNC.Trim（）子串（2，UNC.Trim（）的IndexOf（\\，2） - 2） 坪地看到服务器（如果可用）
bIsReady = IsDriveReady（服务器） 其他
bIsReady = dri.IsReady 万一 只有过程的驱动器已准备好
如果bIsReady = TRUE然后
处理您的驱动器...
MSGBOX（dri.Name＆安培;准备就绪：＆放大器; bIsReady） 万一 下一个 MSGBOX（处理所有驱动器）结束小组专用功能IsDriveReady（BYVAL服务器名称作为字符串）作为布尔
昏暗bReturnStatus由于布尔= FALSE '***设置你的TIMEOUT HERE ***
昏暗的超时为整数= 5'5秒 昏暗pingSender作为新System.Net.NetworkInformation.Ping（）
昏暗的选项作为新System.Net.NetworkInformation.PingOptions（） options.DontFragment = TRUE 输入一个有效的IP地址
昏暗ipAddressOrHostName作为字符串=服务器
昏暗的数据作为字符串=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
昏暗的缓冲区作为字节（）= System.Text.Encoding.ASCII.GetBytes（数据）
昏暗的答复，System.Net.NetworkInformation.PingReply = _
pingSender.Send（ipAddressOrHostName，超时，缓冲，期权） 如果reply.Status = Net.NetworkInformation.IPStatus.Success然后
bReturnStatus = TRUE 万一 返回bReturnStatus
结束功能
解决方案使用线程做检查。我认为，线程可以超时。
I have to check if a set of file paths represent an existing file.
It works fine except when the path contains a network share on a machine that's not on the current network. In this case it takes a pretty long time (30 or 60 seconds) to timeout.
Questions
Is there a way to shorten the timeout for non existing network shares? (I'm certain that when they do exist they'll answer quickly, so a timeout of 1 sec would be fine)
Is there any other way to solve this issue without starting to cache and making the algorithm more complex? (ie, I already know these X network shares don't exist, skip the rest of the matching paths)
UPDATE: Using Threads work, not particularly elegant, though
public bool pathExists(string path) { bool exists = true; Thread t = new Thread ( new ThreadStart(delegate () { exists = System.IO.File.Exists(path); }) ); t.Start(); bool completed = t.Join(500); //half a sec of timeout if (!completed) { exists = false; t.Abort(); } return exists; }This solution avoids the need for a thread per attempt, first check which drives are reachable and store that somewhere.
Experts exchange solution:
First of all, there is a "timeout" value that you can set in the IsDriveReady function. I have it set for 5 seconds, but set it for whatever works for you.
3 methods are used below:
- The first is the WNetGetConnection API function that gets the UNC (\servername\share) of the drive
- The second is our main method: The Button1_Click event
- The third is the IsDriveReady function that pings the server.
This worked great for me! Here you go:
'This API Function will be used to get the UNC of the drive Private Declare Function WNetGetConnection Lib "mpr.dll" Alias _ "WNetGetConnectionA" _ (ByVal lpszLocalName As String, _ ByVal lpszRemoteName As String, _ ByRef cbRemoteName As Int32) As Int32 'This is just a button click event - add code to your appropriate event Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim bIsReady As Boolean = False For Each dri As IO.DriveInfo In IO.DriveInfo.GetDrives() 'If the drive is a Network drive only, then ping it to see if it's ready. If dri.DriveType = IO.DriveType.Network Then 'Get the UNC (\\servername\share) for the ' drive letter returned by dri.Name Dim UNC As String = Space(100) WNetGetConnection(dri.Name.Substring(0, 2), UNC, 100) 'Presuming the drive is mapped \\servername\share ' Parse the servername out of the UNC Dim server As String = _ UNC.Trim().Substring(2, UNC.Trim().IndexOf("\", 2) - 2) 'Ping the server to see if it is available bIsReady = IsDriveReady(server) Else bIsReady = dri.IsReady End If 'Only process drives that are ready If bIsReady = True Then 'Process your drive... MsgBox(dri.Name & " is ready: " & bIsReady) End If Next MsgBox("All drives processed") End Sub Private Function IsDriveReady(ByVal serverName As String) As Boolean Dim bReturnStatus As Boolean = False '*** SET YOUR TIMEOUT HERE *** Dim timeout As Integer = 5 '5 seconds Dim pingSender As New System.Net.NetworkInformation.Ping() Dim options As New System.Net.NetworkInformation.PingOptions() options.DontFragment = True 'Enter a valid ip address Dim ipAddressOrHostName As String = serverName Dim data As String = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" Dim buffer As Byte() = System.Text.Encoding.ASCII.GetBytes(data) Dim reply As System.Net.NetworkInformation.PingReply = _ pingSender.Send(ipAddressOrHostName, timeout, buffer, options) If reply.Status = Net.NetworkInformation.IPStatus.Success Then bReturnStatus = True End If Return bReturnStatus End Function
解决方案Use Threads to do the checks. I think that threads can be timed out.
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