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POWhen Deep Copying a WPF Data Bound Object
 

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  1. POWhen Deep Copying a WPF Data Bound Object
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    <p>I wrote a nifty method to deep copy any object. It does so by recursively calling <code>MemberwiseClone()</code> on any reference type field inside the instance. This method works perfectly on any object I care to use it, including hierarchy relationship objects. The method also sports a dictionary of past visitations so unnecessary duplicate work is avoided. </p> <p>The problem I am having, however, is that this method only works when the object is NOT data bound to WPF/MVVM when a clone is needed. When data bound and the method is invoked, I run into stack overflow exceptions because of (I assume) an established link between <code>INotifyPropertyChanged.PropertyChanged</code> event and the WPF framework. The recursive call then attempts to copy the entire universe of objects including the <code>AppDomain</code> and low-level Pointer objects, which appear to be linked and go on to almost infinity (more than VS2012 can handle, anyway.)</p> <p>I doubt I will ever have need to deep copy an object graph that goes back to the beginning of the <code>AppDomain</code>... is there a smart way to have my copy method "stop" when it reaches a certain boundary? I also thought about simply copying objects before they're data bound, but I'm not sure that's a feasible option, and it's rather silly. I just want a simple deep copy solution that works on types that are not serializable, but are also data-bound via <code>INotifyPropertyChanged</code>.</p> <p>The method's implementation:</p> <pre><code>private static object Clone(object instance, IDictionary&lt;object, object&gt; visitGraph) { var instanceType = instance.GetType(); Debug.WriteLine(instanceType.Name); object clonedInstance = null; if (visitGraph.ContainsKey(instance)) { clonedInstance = visitGraph[instance]; } else { const BindingFlags flags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance; var memberwiseCloneMethod = instanceType.GetMethods(flags).Single(x =&gt; x.Name == "MemberwiseClone" &amp;&amp; !x.GetParameters().Any()); clonedInstance = memberwiseCloneMethod.Invoke(instance, null); visitGraph.Add(instance, clonedInstance); var allReferenceTypeProperties = clonedInstance.GetType().GetAllFields() .Where( x =&gt; !x.FieldType.IsValueType &amp;&amp; x.FieldType != typeof (string)); foreach (var field in allReferenceTypeProperties) { var existingFieldValue = field.GetValue(instance); if (existingFieldValue != null) { var clonedFieldValue = Clone(existingFieldValue, visitGraph); field.SetValue(clonedInstance, clonedFieldValue); } } } return clonedInstance; } public static IEnumerable&lt;FieldInfo&gt; GetAllFields(this Type type) { const BindingFlags flags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance; var fields = type.GetFields(flags); foreach (var field in fields) { yield return field; } if (type.BaseType != null) { foreach (var field in GetAllFields(type.BaseType)) { yield return field; } } } public static object Copy(this object instance) { if (instance == null) throw new ArgumentNullException("instance"); var visitGraph = new Dictionary&lt;object, object&gt;(); var clonedInstance = Clone(instance, visitGraph); return clonedInstance; } </code></pre>
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    1. USakjoshi
    1. USMartin Bliss
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    1. COPosting your method code might make it more clear and helpful in solving your problem.
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      1. USakjoshi
    2. COI disagree, but I'm desperate for an answer. Thanks for the suggestion. :)
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    3. COWhy are you doing this?
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      1. USAmeen
 

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