The primary difference you will notice when working with a web service proxy (as opposed to a regular .NET object) is the speed and internet connectivity requirements. Depending on conditions, a method call on a web service proxy could easily take several seconds to complete. If your computer (or the remote computer) experiences network difficulties, the call might even return a network error message instead of the information you had hoped for.

Example 9-3. Connect-WebService.ps1

##############################################################################

## Connect-WebService.ps1

##

## Connect to a given web service, and create a type that allows you to

## interact with that web service.

##

## Example:

##

##     $wsdl = "http://terraserver.microsoft.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(

    [string] $wsdlLocation = $(throw "Please specify a WSDL location"),

    [string] $namespace,

    [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

[void] [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

}

## There were no errors.  Create the webservice object and return it.

else

{

    ## 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)

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

    $instance

}