Test WebClient API call

Question

I have the following PowerShell script that makes an API Rest GET call.

$FullURL = "http://test.net/config/server/$($env:COMPUTERNAME)?format=test"
$API = New-Object System.Net.WebClient
$APIData = $API.DownloadString($FullURL)
Set-Content -Value $APIdata -Path $APIDataFile -Force

The call is dependent on the local hostname in the URI. It gets the data and exports to a text file as a backup. The problem - the API host maybe down or no information available for the host which will cause all sorts of errors in the script (this is a small part of the script as it adds the data to an XML file).

How do I add logic to the script to test the API call first, if the successfully then continue with making the API call?

It must work for PowerShell 2.0 because of windows 2003 hosts. API is gives an error 404 code if the theres no data.

arco444 · Accepted Answer · 2016-05-17 14:58:02Z

2

You need to use a try/catch block. WebClient should raise an exception when the download isn't successful. Try something like:

$FullURL = "http://test.net/config/server/$($env:COMPUTERNAME)?format=test"
try {
    $API = New-Object System.Net.WebClient
    $APIData = $API.DownloadString($FullURL)
    Set-Content -Value $APIdata -Path $APIDataFile -Force
}
catch [Net.WebException] {
    # Do whatever you want if an exception is raised    
}

edited May 17, 2016 at 14:58

answered May 17, 2016 at 14:45

arco444

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3 Comments

Deano Over a year ago

Thank you for your help. I am getting the following error - Unable to find type [Webexception]: make sure that the assembly containing this type is loaded. I changed the hostname to one that doesnt exist to test. Any ideas

Deano Over a year ago

Thanks, found the Net.webexception in another stackoverflow question as well. Working perfectly. Do you know what [net.webexception] does? just for my learning. Thanks

arco444 Over a year ago

It defines an exception of that type, it doesn't really do anything. Suggest you find an introduction to error handling in .NET, that will go over what exceptions are, when they're thrown and how to handle them. WebException is explained here

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