<Button>
<i:EventTrigger EventName="Click">
<mvvmLight:EventToCommand Command="{Binding MyCommand "/>
</i:EventTrigger>
</Button>
The memory usage will be growing up.
The Attach of the DependencyObject is working fine, but the detach will never called. That causes severe memory issues.
It's a known issue on codeplex:
http://mvvmlight.codeplex.com/workitem/7293http://mvvmlight.codeplex.com/workitem/7512
We tried to find good ways to detach our event handler. But to remove the EventToCommand stuff was much easier than any workaround we found.