GetType.GetProperties - vb.net

Question

I am trying to run through all the controls in a panel and find which properties the user has changed for each control.
So I have this code:
Private Sub WriteProperties(ByVal cntrl As Control)
Try
Dim oType As Type = cntrl.GetType
'Create a new control the same type as cntrl to use it as the default control
Dim newCnt As New Control
newCnt = Activator.CreateInstance(oType)
For Each prop As PropertyInfo In newCnt.GetType().GetProperties
Dim val = cntrl.GetType().GetProperty(prop.Name).GetValue(cntrl, Nothing)
Dim defVal = newCnt.GetType().GetProperty(prop.Name).GetValue(newCnt, Nothing)
If val.Equals(defVal) = False Then
'So if something is different....
End If
Next
Catch ex As Exception
MsgBox("WriteProperties : " & ex.Message)
End Try
End Sub
Now I face three problems:
When the property refers to image (BackGround Image) I have an error :
ImageObject reference not set to an instance of an object.
The second problem is that the code:
If val.Equals(defVal) = False Then
'So if something is different....
End If
is executes sometimes when the val and defVal are the same.
This is happening in cases that the property is a "parentProperty" like FlatAppearance (which has more child properties)
My loop doesn't look into basic properties like Size, or Location which I want

Answer 1

Re: Not set to an instance of an object, do something like ...
If val IsNot Nothing AndAlso defVal IsNot Nothing AndAlso Not val.Equals(defVal) Then
Which will only do the comparison if neither value is Nothing (aka Null).
Unfortunately, #2 is a fundamental problem - .Equals by default checks if the 2 object references point at the same object in memory - eg if You did
Dim A As New SomeClass
Dim B As New SomeClass
If A.Equals(B) Then
...
End If
Would return False unless SomeClass has an overridden equality comparer, which many classes do not.
You could check if the value in question is a type you know you can compare (Integer, String, Double, etc). If not, you could iterate through its properties and perform the same check again. This would allow you to compare the public properties of any type for equality but wouldn't guarantee the internal state of the classes is the same.
Something Like (Untested/Pseudo)...
Function Compare (PropA, PropB) As Boolean
Dim Match = True
If PropA.Value Is Nothing Or PropB.Value Is Nothing
Match = False
Else
If PropA.Value.GetType.IsAssignableFrom(GetType(String)) Or
PropA.Value.GetType.IsAssignableFrom(GetType(Integer)) Or ... Then
Match = PropB.Value.Equals(PropB.Value)
Else
For Each Prop In PropA.Value.GetType.GetProperties()
Match = Compare(Prop, PropB.Value.GetType.GetProperty(Prop.Name))
If Not Match Then Exit For
Next
End If
End If
Return Match
End Function
This is still not ideal as the internal states of the values may differ.