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POWP7 IsolatedStorage XML file empty after app update
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  1. POWP7 IsolatedStorage XML file empty after app update
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    copied!<p>I submitted an update for my WP7 app and I've had users complain that their data was erased after the update. I am storing my data by serializing my ViewModel class as an XML file in IsolatedStorage. During my testing I noticed that updating the app caused the settings file to get partially overwritten with a serialized copy of a new instance (with default values) of my ViewModel object. I thought I had solved the problem by using FileMode.Create when I write to my XML file, but I guess not. </p> <p>Could the serialization have gone wrong because I added new properties to the ViewModel object and deserializing from the existing XML file failed? I do have my code set to instantiate a new ViewModel object if one cannot be read from the XML file. If this is the case, does it mean I cannot add any new properties to my ViewModel object?</p> <p>Edit:<br> Here is the structure of my ViewModel, not really all that complex: </p> <pre><code>public class MyClass: INotifyPropertyChanged { public MyClass() { // Set defaults this.Items= new ObservableCollection&lt;Item&gt;(); this.TextTemplate = "default"; this.HasSeenSomething = false; } public ObservableCollection&lt;Item&gt; Items { get; set; } // New properties added in app update public string TextTemplate { get; set; } public bool HasSeenSomething { get; set; } } </code></pre> <p>Here is the code I'm using to serialize/deserialize my ViewModel. I think it is pretty standard but maybe I've botched something: </p> <pre><code>public static void WriteToXml&lt;T&gt;(T data, string path) { var xmlWriterSettings = new XmlWriterSettings { Indent = true }; using (var myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication()) { using (var stream = myIsolatedStorage.OpenFile(path, FileMode.Create)) { var serializer = new XmlSerializer(typeof(T)); using (var xmlWriter = XmlWriter.Create(stream, xmlWriterSettings)) { serializer.Serialize(xmlWriter, data); } } } } public static T ReadFromXml&lt;T&gt;(string path) { T data = default(T); try { using (var myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication()) { if (myIsolatedStorage.FileExists(path)) { using (var stream = myIsolatedStorage.OpenFile(path, FileMode.Open)) { try { var serializer = new XmlSerializer(typeof(T)); object instance = serializer.Deserialize(stream); if (instance != null) data = (T)instance; } catch (System.Exception ex) { var e = ex; } } } } } catch(System.Exception ex) { var e = ex; } return data; } </code></pre>
 

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