PowerShell无法从ASP.NET DLL调用简单函数

Question

I'm trying to call this really simple .NET 4 function with PowerShell v2. Its definition look like:

Public Shared Function currentSchoolYear() As String Member of NM4.SiteAdmin.Logic.Subscription

Let's add the path to the DLL file containing that function. It's an ASP.NET MVC web application DLL file.

PS > Add-Type -Path C:\\xxx\\bin\\xxxWebApp.dll

Let's try it (FAIL!):

PS >
[NM4.SiteAdmin.Logic.Subscription]::currentSchoolYear()
Exception calling "currentSchoolYear"
with "0" argument(s): "The type
initializer for
'NM4.SiteAdmin.Logic.Subscription'
threw an exception." At line:1 char:54
+ [NM4.SiteAdmin.Logic.Subscription]::currentSchoolYear
<<<< ()
+ CategoryInfo : NotSpecified: (:) [],
MethodInvocationException
+ FullyQualifiedErrorId : DotNetMethodException

Let's observe the class from PowerShell:

PS >
[NM4.SiteAdmin.Logic.Subscription]

IsPublic IsSerial Name
BaseType

-------- -------- ---- -------- True False Subscription
System.Object

Let's observe the function from PowerShell

PS >
[NM4.SiteAdmin.Logic.Subscription]::currentSchoolYear


MemberType : Method
OverloadDefinitions : {static string
currentSchoolYear()} TypeNameOfValue
:
System.Management.Automation.PSMethod
Value : static string
currentSchoolYear() Name
: currentSchoolYear IsInstance
: True

Why oh why? It seems like the doc to me.

Answer 1

I used this command to get more details about the error:

$error | Format-List -force

Which then throwed this more precise example:

System.NullReferenceException: Object
reference not set to an instance of an
object.
at
NM4.SiteAdmin.GlobalFunctions.EstMachineProduction()
in
C:\\xxx\\Old_App_Code\\DataModel\\GlobalFunctions.vb:line
17

And I discovered it was a call to the web.config that failed:

Return
ConfigurationManager.ConnectionStrings.Item("test_DBNM4").ConnectionString

DLL files loaded by PowerShell are probably not in their usual web context. I hardcoded a ConnectionString to test it (temporary, not a good security practice), and it's working.

Answer 2

It sounds like an exception in the static constructor OR a type on which NM4.SiteAdmin.Logic.Subscription depends could not be loaded. I'm assuming "C:\\xxx\\bin\\xxxWebApp.dll" and friends aren't in GAC and you're not running from "C:\\xxx\\bin\\" so therefore powershell can't resolve the dependencies. Try running this from "C:\\xxx\\bin\\".