Using PowerShell to execute a dynamic WebMethod

Question

I have a nice little powershell script that works

$URL = $args[0]
$proxy = New-WebServiceProxy -Uri $URL -Namespace webservice -UseDefaultCredential
$result = $proxy.TestWebMethod()

usage from cmd: 
powershell.exe myscript.ps1 "http://somesite.com/someservice.asmx"

What I want to do is also be able to pass in the method name dynamically, something to the effect of:

$URL = $args[0]
$proxy = New-WebServiceProxy -Uri $URL -Namespace webservice -UseDefaultCredential
$result = $proxy.$args[1]

usage from cmd: 
powershell.exe myscript.ps1 "http://somesite.com/someservice.asmx" "TestWebMethod"

Is there some way to make it work dynamically the second way?

Keith Hill · Accepted Answer · 2013-11-07 21:32:00Z

1

It is a little odd looking but in PowerShell V3 you can do this:

$proxy | Foreach $args[1]

You can also do it like this if the method takes no arguments:

$proxy."$args[1]"

And if you have arguments to the method:

$proxy."$args[1]".Invoke(<args here>)

Here's an example on V2 that uses a web service and takes an arg:

$URI = "http://www.webservicex.net/uszip.asmx?WSDL"
$zip = New-WebServiceProxy -uri $URI -namespace WebServiceProxy -class ZipClass
$method = "GetInfoByZIP"
$zip."$method".Invoke('80525')

edited Nov 7, 2013 at 21:32

answered Nov 7, 2013 at 20:22

Keith Hill

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5 Comments

kralco626 Over a year ago

I like the idea, but I can't get it to work. For testing I stored the method in a variable: $Method = "TestWebMethod" and then I tried $proxy.$Method" and nothing happened it just returned to the next line. $proxy | Foreach $Method returned an error.

Keith Hill Over a year ago

The first approach only works on PowerShell v3. You must on v1 or v2. With the quoted version on V2 do it this way $proxy."$method".Invoke().

kralco626 Over a year ago

Got Error: you cannot call a method on a null valued expression.

kralco626 Over a year ago

I would rather do it this way, just because it's simpler, but as of right now I can only get it to work using iex

Keith Hill Over a year ago

Nevermind, you must be on at least V2 to use New-WebServiceProxy. Weird, I tested on V2 and that approach worked for me.

Frode F. · Accepted Answer · 2013-11-07 21:33:59Z

1

I don't have a service to test with, but have you tried invoke-expression (iex)?

$result = iex "`$proxy.$($args[1])()"

edited Nov 7, 2013 at 21:33

answered Nov 7, 2013 at 20:19

Frode F.

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4 Comments

kralco626 Over a year ago

$Method = "TestWebMethod" and then iex "$proxy.$($Method)()" return an error An expression was expected after '('.`

kralco626 Over a year ago

I was able to use iex but had to do it on two lines using a single quote. >$serviceCall = '$proxy.' + $($args[1]) + '()' >$result = iex $serviceCall

kralco626 Over a year ago

One line version: $result = iex $('$proxy.' + $($args[1]) + '()')

Frode F. Over a year ago

My solution worked for me for calling the toUpper() function on a string. You may need to escape the $proxy variable. See updated answer

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