我正在编写一个powershell脚本来调用一个RESTful API，我需要解析响应。我在解析响应时遇到了麻烦，因为数组没有一个键名。API只返回数组的内容：

[
    {
        "ProfileId": "b9b4bf0b-fea3-4464-af91-b79b521d36ba",
        "SourcePhoneNumber": "8880001111",
        "FirstName": "Peter"
    },
    {
        "ProfileId": "b9b4bf1b-cta3-4464-af91-b68c521d36ba",
        "SourcePhoneNumber": "8660001111",
        "FirstName": "Fred"
    }
]

下面是调用API并获得响应的方法：

$headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headers.Add("content-type", "application/json")
$headers.Add("Accept-Language", "en-US")
$headers.Add("Authorization", "OAuth $AccessToken")

$response = Invoke-RestMethod "$($privateApiUrl)/api/v1/profiles" -Headers $headers -Method Get -ErrorVariable RestError -ErrorAction SilentlyContinue

if ($RestError)
{
    $HttpStatusCode = $RestError.ErrorRecord.Exception.Response.StatusCode.value__
    $HttpStatusDescription = $RestError.ErrorRecord.Exception.Response.StatusDescription

    Throw "Http Status Code: $($HttpStatusCode) `nHttp Status Description: $($HttpStatusDescription)"
}
else {
    Write-Host $response

    #Need to parse the first ProfileId out of the response here
    $json = ConvertTo-Json -InputObject @( $response )

    Write-Host $json[0].ProfileId #This outputs nothing

    $response | Out-File -FilePath c:\response2.txt
}

倒数第二行“Write-Host $json[0]...”是我希望访问ProfileID的位置。
响应被写入c：\response2.txt，因此我知道API请求正在工作，并且我从API调用中获得了良好的数据。
那么，我在访问对象的ProfileId时做错了什么呢？