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.
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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: 1. The first is the WNetGetConnection API function that gets the UNC (\servername\share) of the drive 2. The second is our main method: The Button1_Click event 3. 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
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