Cannot open sharepoint UNC path unless already opened through Windows Explorer

Question

I'm hoping somebody can shed light on this, because it has been driving me to distraction.

I have a script which will save the reports it creates to a sharepoint document library via UNC path, if the path exists, otherwise it saves to the UNC path of a network drive location as a fallback.

I've noticed that checking with test-path, saving (through an msexcel COM object) or trying to open the folder in windows explorer using invoke-item only work if I had already accessed the sharepoint site (via web browser or windows explorer) since the PC last logged on (I'm running Windows 7 Enterprise Service Pack 1 - 64-bit edition).

If I haven't yet been on to sharepoint manually since last logon, test-path returns false, and the other methods cause ItemNotFoundException e.g.

ii : Cannot find path '\\uk.sharepoint.mydomain.local\sites\mycompany\myteam\Shared Documents\Reports' because it does not exist.
At line:1 char:1
+ ii '\\uk.sharepoint.mydomain.local\sites\mycompany\myteam\Shared Document ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (\\uk.sharepoint...\Reports:String) [Invoke-Item], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.InvokeItemCommand

Example areas of code:

$LANPath = "\\myserver\myshare\teamdirs\scriptdir"
$SharepointPath = "\\uk.sharepoint.mydomain.local\sites\mycompany\myteam\Shared Documents\Reoprts"
$ScriptPath = $LANPath + "\bin"
If (Test-Path $SharepointPath) {$BasePath = $SharepointPath;write-host "Using sharepoint to save reports"} else {$BasePath = "$LANPath\Reports";write-host "Using LAN to save reports - sharepoint not accessible"}

and

$_|select -expandproperty HTMLBody | Out-File $($BasePath + "\Eml_body.html")
    Write-Host "Reformating HTML"
    $html = New-Object -ComObject "HTMLFile";
    $source = Get-Content -Path ($BasePath + "\Eml_body.html") -Raw;

and when saving the excel spreadsheet from within my COM object:

$workbook._SaveAs($fileout,[Microsoft.Office.Interop.Excel.XlFileFormat]::xlOpenXMLWorkbook,$Missing,$Missing,$false,$false,[Microsoft.Office.Interop.Excel.XlSaveAsAccessMode]::xlNoChange,[Microsoft.Office.Interop.Excel.XlSaveConflictResolution]::xlLocalSessionChanges,$true,$Missing,$Missing)

I have a feeling the WebClient service will be able to help you out. $webclient = New-Object System.Net.WebClient This is the service used by Windows Explorer to access SharePoint locations. For reference: msdn.microsoft.com/en-us/library/… — Thriggle
@Thriggle Ah, of course, it's a webserver running WebDAV, not a fileserver. Walks like a duck, quacks like a duck....not a duck! I had a play with webclient but couldn't get it to authenticate when setting UseDefaultCredentials to true. Instead, I've gone with Invoke-WebRequest as that should be enough to get the site into the WebDAV cache and thereafter UNC paths should work. If you post up as an answer I'll mark as answer accordingly. Syntax I used was Invoke-WebRequest -Uri "http://uk.sharepoint.mydomain.local/sites/mycompany/myteame/Shared Documents/Reports" -UseDefaultCredentials — Graham Gold
Scratch that - Invoke-WebRequest works for accessing the site but because it isn't using the UNC path, it's not invoking WebDAV, so I need to revisit WebClient and suss out why UseDefaultCredentials results in an authentication error - some more googling and searching of SO awaits — Graham Gold
Based on this remark on the WebClient.Credentials documentation, the DefaultCredentials may be those of the ASP.NET worker process, which wouldn't necessarily have access to the files: If the WebClient class is being used in a middle tier application, such as an ASP.NET application, the DefaultCredentials belong to the account running the ASP page (the server-side credentials). Typically, you would set this property to the credentials of the client on whose behalf the request is made. — Thriggle

Thriggle Thriggle · Accepted Answer · 2016-04-07T14:26:18

You should be able to use a System.Net.WebClient object to access SharePoint file locations.

$client = New-Object System.Net.WebClient

The documentation for the WebClient.Credentials property suggests that the default credentials in this case may be for the ASP.NET server-side process rather than the current user's credentials:

If the WebClient class is being used in a middle tier application, such as an ASP.NET application, the DefaultCredentials belong to the account running the ASP page (the server-side credentials). Typically, you would set this property to the credentials of the client on whose behalf the request is made.

You therefore may want to set the credentials manually. You can plug them in as plain text...

$client.Credentials = New-Object System.Net.NetworkCredential("username","pswd","domain")

...or you could prompt the current user for their credentials.

$client.Credentials = Get-Credential

Here's an example that grabs a file and writes its content to the screen:

$client = New-Object System.Net.WebClient
$client.Credentials = Get-Credential

$data = $client.OpenRead("http://yoursharepointurl.com/library/document.txt")
$reader = New-Object System.IO.StreamReader($data)
$results = $reader.ReadToEnd()
Write-Host $results
$data.Close()
$reader.Close()

Cannot open sharepoint UNC path unless already opened through Windows Explorer

2 Answers