What's this? [field:SecurityCritical]
<p>Looking at System.Windows.Threading.Dispatcher (as decompiled by Reflector) I came across;</p>

<pre><code>[field: SecurityCritical]
public event DispatcherUnhandledExceptionFilterEventHandler UnhandledExceptionFilter;
</code></pre>

<p>I don't recognize the 'field' part of the attribute declaration, what is it?</p>

<p><strong>Edit:</strong></p>

<p>This is how it appears in the reference source:</p>

<pre><code>    public event DispatcherUnhandledExceptionFilterEventHandler UnhandledExceptionFilter
    { 
        [SecurityCritical] 
        [UIPermissionAttribute(SecurityAction.LinkDemand,Unrestricted=true)]
        add 
        {
            _unhandledExceptionFilter += value;
        }
        [SecurityCritical] 
        [UIPermissionAttribute(SecurityAction.LinkDemand,Unrestricted=true)]
        remove 
        { 
            _unhandledExceptionFilter -= value;
        } 
    }
</code></pre>
