Get-WMIObject To be or not to be -- a collection or an object

Consider this code:

$mystr = ""
$ws = new-object -comobject WScript.Shell
$path = $ws.CurrentDirectory + "\Win32_Process.csv"
$fso = new-object -comobject Scripting.FileSystemObject
$txtstream = $fso.OpenTextFile($path, 2, $true, -2)
$moc = Get-WMIObject -namespace root\cimv2 -class Win32_Process
$mocEnum = $moc.GetType().InvokeMember('GetEnumerator', 'InvokeMethod',$Null, $moc, $Null)
while($mocEnum.MoveNext())
{
    $obj =  $mocEnum.Current
    foreach($prop in $obj.Properties)
    {  
        if($mystr -ne "")
        {
            $mystr += ","
        }
        $mystr += $prop.Name 
    }
    $txtstream.WriteLine($mystr)
    $mystr = ""
    break     
}
$mocEnum.Reset()

while($mocEnum.MoveNext())
{
    $obj = $mocEnum.Current
    foreach($prop in $obj.Properties)
    {  
        if($mystr -ne "")
        {
            $mystr += ","
        }
        $tstr = '"'
        $tstr += $prop.value
        $tstr += '"'
        $mystr += $tstr 
    }
    $txtstream.WriteLine($mystr)
    $mystr = ""        
} 

As it stands, this code works well to create a csv file.  And, yes, you can do the same using the PSObject. The problem is, the code assumes the Get-WMIObject will return a collection of objects and in some cases it will not.

Exception calling "InvokeMember" with "5" argument(s): "Method 'System.Management.ManagementObject.GetEnumerator' not found."
At C:\Users\Administrator\Desktop\Test.ps1:2 char:39
+ $mocEnum = $moc.GetType().InvokeMember <<<< ('GetEnumerator', 'InvokeMethod',$Null, $moc, $Null)
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : DotNetMethodException
You cannot call a method on a null-valued expression.
At C:\Users\Administrator\Desktop\Test.ps1:3 char:24
+ while($mocEnum.MoveNext <<<< ())
+ CategoryInfo : InvalidOperation: (MoveNext:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull


And, by the way, the code works fine using foreach enumerations of the objects.