class SomeClass
    {
        [String]$Message
        [int]$Counter
    };
$SomeObject = [SomeClass]('{    "Message":  "test Message",    "Counter":  1}' | ConvertFrom-Json);

Write-Host $SomeObject.Message " => " $SomeObject.Counter;

$SomeObjects = [SomeClass[]]('[{    "Message":  "test Message 1",    "Counter":  1}, {    "Message":  "test Message 2",    "Counter":  2}]' | ConvertFrom-Json);

Write-Host $SomeObjects[0].Message " => " $SomeObjects[0].Counter;
Write-Host $SomeObjects[1].Message " => " $SomeObjects[1].Counter;