Public
	Sub AddQueryClose(h As FormClosingHandler)
		If IsNothing(queryClose) Then
			queryClose = h
		Else
			queryClose += h
		End If
	End Sub
	Sub RemoveQueryClose(h As FormClosingHandler)
		If Not IsNothing(queryClose) Then
			queryClose -= h
		End If
	End Sub
Protected
	Function OnQueryClose(e As FormClosingArgs) As Boolean
		If Not IsNothing(queryClose) Then
			queryClose(This, e)
			Return True
		End If
	End Function
Private
	queryClose As FormClosingHandler