Connect to a Web Service in PowerShell

##############################################################################
##
## Connect-WebService
##
## From Windows PowerShell Cookbook (O'Reilly)
## by Lee Holmes (http://www.leeholmes.com/guide)
##
## Connect to a given web service, and create a type that allows you to
## interact with that web service. In PowerShell version two, use the
## New-WebserviceProxy cmdlet.
##
## Example:
##
## $wsdl = "http://www.terraserver-usa.com/TerraService2.asmx?WSDL"
## $terraServer = Connect-WebService $wsdl
## $place = New-Object Place
## $place.City = "Redmond"
## $place.State = "WA"
## $place.Country = "USA"
## $facts = $terraserver.GetPlaceFacts($place)
## $facts.Center
##
##############################################################################

param(
    ## The URL that contains the WSDL
    [string] $WsdlLocation = $(throw "Please specify a WSDL location"),

    ## The namespace to use to contain the web service proxy
    [string] $Namespace,

    ## Switch to identify web services that require authentication
    [Switch] $RequiresAuthentication
)

## Create the web service cache, if it doesn't already exist
if (-not (Test-Path Variable:\Lee.Holmes.WebServiceCache))
{
    ${GLOBAL:Lee.Holmes.WebServiceCache} = @{}
}

## Check if there was an instance from a previous connection to
## this web service. If so, return that instead.
$oldInstance = ${GLOBAL:Lee.Holmes.WebServiceCache}[$wsdlLocation]
if ($oldInstance)
{
    $oldInstance
    return
}

## Load the required Web Services DLL
$null = [Reflection.Assembly]::LoadWithPartialName("System.Web.Services")

## Download the WSDL for the service, and create a service description from
## it.
$wc = New-Object System.Net.WebClient

if($requiresAuthentication)
{
    $wc.UseDefaultCredentials = $true
}

$wsdlStream = $wc.OpenRead($wsdlLocation)

## Ensure that we were able to fetch the WSDL
if (-not (Test-Path Variable:\wsdlStream))
{
    return
}

$serviceDescription = [Web.Services.Description.ServiceDescription]::Read($wsdlStream)
$wsdlStream.Close()

## Ensure that we were able to read the WSDL into a service description
if (-not (Test-Path Variable:\serviceDescription))
{
    return
}

## Import the web service into a CodeDom
$serviceNamespace = New-Object System.CodeDom.CodeNamespace
if ($namespace)
{
    $serviceNamespace.Name = $namespace
}

$codeCompileUnit = New-Object System.CodeDom.CodeCompileUnit
$serviceDescriptionImporter = New-Object Web.Services.Description.ServiceDescriptionImporter
$serviceDescriptionImporter.AddServiceDescription($serviceDescription, $null, $null)
[void] $codeCompileUnit.Namespaces.Add($serviceNamespace)
[void] $serviceDescriptionImporter.Import($serviceNamespace, $codeCompileUnit)

## Generate the code from that CodeDom into a string
$generatedCode = New-Object Text.StringBuilder
$stringWriter = New-Object IO.StringWriter $generatedCode
$provider = New-Object Microsoft.CSharp.CSharpCodeProvider
$provider.GenerateCodeFromCompileUnit($codeCompileUnit, $stringWriter, $null)

## Compile the source code.
$references = @("System.dll", "System.Web.Services.dll", "System.Xml.dll")
$compilerParameters = New-Object System.CodeDom.Compiler.CompilerParameters
$compilerParameters.ReferencedAssemblies.AddRange($references)
$compilerParameters.GenerateInMemory = $true

$compilerResults = $provider.CompileAssemblyFromSource($compilerParameters, $generatedCode)

## Write any errors if generated.
if ($compilerResults.Errors.Count -gt 0)
{
    $errorLines = ""
    foreach($error in $compilerResults.Errors)
    {
        $errorLines += "`n`t" + $error.Line + ":`t" + $error.ErrorText
    }

    Write-Error $errorLines
    return
}
else
{
    ## There were no errors. Create the webservice object and return it.

    ## Get the assembly that we just compiled
    $assembly = $compilerResults.CompiledAssembly

    ## Find the type that had the WebServiceBindingAttribute.
    ## There may be other "helper types" in this file, but they will
    ## not have this attribute
    $type = $assembly.GetTypes() |
        Where-Object { $_.GetCustomAttributes(
            [System.Web.Services.WebServiceBindingAttribute], $false) }

    if (-not $type)
    {
        Write-Error "Could not generate web service proxy."
        return
    }

    ## Create an instance of the type, store it in the cache,
    ## and return it to the user.
    $instance = $assembly.CreateInstance($type)

    ## Many services that support authentication also require it on the
    ## resulting objects
    if ($requiresAuthentication)
    {
        if (@($instance.PsObject.Properties |
            where { $_.Name -eq "UseDefaultCredentials" }).Count -eq 1)
        {
            $instance.UseDefaultCredentials = $true
        }
    }

    ${GLOBAL:Lee.Holmes.WebServiceCache}[$wsdlLocation] = $instance

    $instance
}