I want to create an output with all the Azure AD applications, which returns a)listing of all b) listing of expiring apps

This is what I have so far, but the $expirationlist doesn't return back a listing of ALL the applications expiring with the $expirationlist variable.

$date= get-date
$expirationdate= $date.AddDays(30)
$ADApplications = Get-AzADApplication 
$result = foreach ($application in $ADApplications)
{
$credentials = Get-AzADAppCredential -ApplicationId 
$application.ApplicationId 
$StartDate = $credentials.StartDate
$EndDate = $credentials.EndDate



[PSCustomObject]@{
    ApplicationName = $application.DisplayName
    ApplicationID = $application.ApplicationId
    ObjectID = $application.ObjectId
    CreationDate = $StartDate
    ExpirationDate = $EndDate
   

}
if($EndDate -lt $expirationdate)
   {
        $expirationlist = [PSCustomObject]@{
       ApplicationName = $application.DisplayName
       ApplicationID = $application.ApplicationId
        ObjectID = $application.ObjectId
        CreationDate = $StartDate
        ExpirationDate = $EndDate  
        }
    }
}
$expirationlist

The error comes from casting a PSCustomObject with a $null key:

Example:

PS /> [pscustomobject]@{ $null = 'asd' }
A null key is not allowed in a hash literal.
At line:1 char:19
+ [pscustomobject]@{ $null = 'asd' }
+                    ~~~~~
    + CategoryInfo          : InvalidOperation: (System.Collecti...deredDictionary:OrderedDictionary) [], RuntimeException
    + FullyQualifiedErrorId : InvalidNullKey

Since these variables are not defined they are basically null:

$ApplicationName, $ApplicationID, $ObjectID, etc.

Try with this, it should work, I also added a minor efficiency improvement:

$ADApplications = Get-AzADApplication
$result = foreach ($application in $ADApplications)
{
    $credentials = Get-AzADAppCredential -ApplicationId $application.ApplicationId 
    
    foreach($credential in $credentials)
    {
        $StartDate = $credential.StartDate
        $EndDate = $credential.EndDate
    
        [PSCustomObject]@{
            ApplicationName = $application.DisplayName
            ApplicationID = $application.ApplicationId
            ObjectID = $application.ObjectId
            CreationDate = $StartDate
            ExpirationDate = $EndDate
        }
    }
}

$result | Where-Object {[datetime]$_.EndDate -lt [datetime]::Now.AddDays(30)}