How to fetch an attribute value from xml using powershell?

Assuming your XML structure is something similar to:

$xml = [xml]'
<Events>
<Event Definition="Validate" DLLPath="" DLLName="Helper.dll" DLLClass="HelpMain" DLLRoutine="pgFeatureInfoOnValidate_WriteToRegSelectedFeatures" InputParameters="pTreeViewFeatureTreeServerOS" RunOnce="no"/>
<Event Definition="Validate1" DLLPath="" DLLName="Helper.dll1" DLLClass="HelpMain1" DLLRoutine="pgFeatureInfoOnValidate_WriteToRegSelectedFeatures" InputParameters="pTreeViewFeatureTreeServerOS" RunOnce="no"/>
</Events>
'

#Or get it from a XML file
$xml = [xml](Get-Content $XMLPath)

$xml.Events.Event | Select DLLName