Powershell New-WebServiceProxy Async methods

Question

I have a WCF library exposing some useful information and I query them from powershell with New-WebServiceProxy cmdlet

$link = "http://localhost/Rlib/Rlib.Info.svc";
$service = New-WebServiceProxy -Uri $link;

Assume I have a function like GetLastData(), I usually invoke it this way

$service.GetLastData()

Now I've a very slow function that requires lot of time to complete (complex DB query that return a date), I see that an Async function is automatically generated and I can Invoke it using $service.GetLastDataAsync(). How does it work? Once I call the async method how can I check if data are available and recover them?

Does the $service object have a GetLastDataCompleted event as well? — Mathias R. Jessen
– Mathias R. Jessen, Commented May 13, 2015 at 13:04

Mathias R. Jessen · Accepted Answer · 2015-05-13 14:08:31Z

3

After you call the Async method, a corresponding event will be raised when the operation is finished (in your case GetLastDataCompleted).

You can use Register-ObjectEvent to "listen" for when this event is raised!

I used CDYNE's IP2Geo service for a quick test, but the idea is exactly the same with any other SOAP service:

$ServiceUri = 'http://ws.cdyne.com/ip2geo/ip2geo.asmx?wsdl'
$Service = New-WebServiceProxy -Uri $ServiceUri

# Make sure the environment is clean
Remove-Variable -Scope Global -Name IPResult -Force | Out-Null
Unregister-Event -SourceIdentifier "IPResolved"

# Register an event subscription
Register-ObjectEvent -InputObject $Service -EventName ResolveIPCompleted -SourceIdentifier "IPResolved" -Action { $Global:IPResult = $args[1] } | Out-Null

# Initialize the operation with Async
$Service.ResolveIPAsync('8.8.8.8','')

# Do other stuff in the background here

# Wait for the variable to get populated
while(-not(Get-Variable -Scope Global -Name IPResult -ErrorAction SilentlyContinue)){
    Start-Sleep -Seconds 1
}

# Let's see what we got!
if($Global:IPResult.Error -eq $null){
    Write-Host "Success!"

    # The Result property holds the result from the operation
    $Global:IPResult.Result

} else {
    Write-Host "Failed!"
}

edited May 13, 2015 at 14:08

answered May 13, 2015 at 13:58

Mathias R. Jessen

178k13 gold badges175 silver badges234 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Erti-Chris Eelmaa Over a year ago

It would be far easier just to poll the Task.IsCompleted property (from ResolveIPAsync)

Erti-Chris Eelmaa · Accepted Answer · 2015-05-13 12:51:24Z

2

How does it work?

GetLastDataAsync returns Task<something>, which can be used to track the process of an out-going operation. It can get quite complicated. You probably don't need to use async version, unless you have good reason to? You can use powershell jobs for synchronous version, and just poll how the job is doing.

Once I call the async method how can I check if data are available and recover them?

If you would like to wait for result, you could do GetLastDataAsync(..).Result, but this would be useless, as you can already use the synchronous one.

There is no easy way in my opinion to consume Task correctly. The closest I found was to use some kind of custom DLL, in this manner:

    C:\PS> $path = "$home\Pictures\foo.png"
    C:\PS> $asyncOp = [Windows.Storage.StorageFile]::GetFileFromPathAsync($path)
    C:\PS> Add-Type -Path ~\PoshWinRT.dll
    C:\PS> $typeName = 'PoshWinRT.AsyncOperationWrapper[Windows.Storage.StorageFile]'
    C:\PS> $wrapper = new-object $typeName -Arg $asyncOp
    C:\PS> $file = $wrapper.AwaitResult()
    C:\PS> $file

The theory behind wrapper is that it's using Task.Wait behind the scenes, which kind of beats the whole purpose of async. As it's still blocking the main thread.

TLDR; stick with synchronized version & scheduled jobs if you need.

https://rkeithhill.wordpress.com/2013/09/30/calling-winrt-async-methods-from-windows-powershell/

answered May 13, 2015 at 12:51

Erti-Chris Eelmaa

26.6k6 gold badges65 silver badges83 bronze badges

1 Comment

Naigel Over a year ago

Thank you for the complete explanation. I think using New-Job on the synchronous method is a much more viable solution for my situation

Collectives™ on Stack Overflow

Powershell New-WebServiceProxy Async methods

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related