How to serialize an observablecollection of type entity to xml

Question

I'm working with VS 2015 on a WPF application using Entity Framework. In this application I have in one of my WPF window the possibility to serialize a canvas on which I got some custom controls.

Today I tried to add to one of my custom controls a new dependencyproperty which is an observablecollection which type is an entity (in my case a table called Formulas).

Normally it's not possible to serialize generic types.

So I added a new class to my app and used that in my code as property type.

public class AssignedFormulasCollection : ObservableCollection<Formulas>
{
    public AssignedFormulasCollection()
    {
    }

    public AssignedFormulasCollection(List<Formulas> list) : base(list)
    {
    }
}

This is the code of the entity Formulas:

public partial class Formulas
{
    public Formulas()
    {
        this.Formula_Attributes = new HashSet<Formula_Attributes>();
        this.Formula_Field_Attributes = new HashSet<Formula_Field_Attributes>();
        this.Input_Field_Formulas = new HashSet<Input_Field_Formulas>();
        this.Stepfunctions = new HashSet<Stepfunctions>();
    }

    public int formula_id { get; set; }
    public int description_id { get; set; }
    public string formula_name { get; set; }
    public string formula_version { get; set; }
    public string formula_expression { get; set; }
    public string formula_type { get; set; }
    public Nullable<float> result1 { get; set; }
    public Nullable<float> result2 { get; set; }
    public Nullable<float> result3 { get; set; }
    public Nullable<int> version { get; set; }
    public string changer { get; set; }
    public Nullable<System.DateTime> change_date { get; set; }

    public virtual Descriptions Descriptions { get; set; }
    public virtual ICollection<Formula_Attributes> Formula_Attributes { get; set; }
    public virtual ICollection<Formula_Field_Attributes> Formula_Field_Attributes { get; set; }
    public virtual ICollection<Input_Field_Formulas> Input_Field_Formulas { get; set; }
    public virtual ICollection<Stepfunctions> Stepfunctions { get; set; }
}

I serialize the canvas by this method:

public string SerializeControlToXaml(FrameworkElement element)
{
    var elementToXaml = new StringBuilder();
    var settings = new XmlWriterSettings();
    settings.Indent = true;
    settings.OmitXmlDeclaration = true;
    var serializationManager = new 
XamlDesignerSerializationManager(XmlWriter.Create(elementToXaml, settings));
    serializationManager.XamlWriterMode = XamlWriterMode.Expression;
    XamlWriter.Save(element, serializationManager);
    var xaml = elementToXaml.ToString();

    return xaml;
}

But when I try to serialize the canvas with the custom controls I get the following error message:

System.Reflection.TargetInvocationException was not handled by user code.
HResult = -2146232828
Message = The PropertyAccessorDescriptions for the System.Data.Entity.DynamicProxies.Formulas_CF5776A4E794BA378BEBDBE1E29E7967B4AACCF844AB5416006C852677145A0A object caused the following exception: The ObjectContext instance was discarded and can no longer be used for transactions that require a connection.

Source = System

StackTrace:
At System.ComponentModel.ReflectPropertyDescriptor.GetValue (Object component)
At System.Windows.Markup.Primitives.ElementProperty.get_Value ()
At System.Windows.Markup.Primitives.ElementPropertyBase.get_IsComposite ()
At System.Windows.Markup.Primitives.MarkupWriter.RecordNamespaces (ScopeScope, MarkupObject item, IValueSerializerContext context, Boolean lastWasString)
At System.Windows.Markup.Primitives.MarkupWriter.RecordNamespaces (ScopeScope, MarkupObject item, IValueSerializerContext context, Boolean lastWasString) At System.Windows.Markup.Primitives.MarkupWriter.RecordNamespaces (ScopeScope, MarkupObject item, IValueSerializerContext context, Boolean lastWasString) At System.Windows.Markup.Primitives.MarkupWriter.RecordNamespaces (ScopeScope, MarkupObject item, IValueSerializerContext context, Boolean lastWasString) At System.Windows.Markup.Primitives.MarkupWriter.WriteItem (MarkupObject item) At System.Windows.Markup.Primitives.MarkupWriter.SaveAsXml (XmlWriter writer, MarkupObject item) At System.Windows.Markup.Primitives.MarkupWriter.SaveAsXml (XmlWriter writer, Object instance, XamlDesignerSerializationManager manager) At System.Windows.Markup.XamlWriter.Save (Object obj, XamlDesignerSerializationManager manager) At P16Common.XamlDeSerializer.SerializeControlToXaml (FrameworkElement element) in C: \ svn_checkout \ P16_RoeV \ Sourcen \ P16Admintool_develop \ P16Common \ XamlDeSerializer.cs: Line 50. At P16Common.CommonMethods.SerializeToXml (FrameworkElement designerGrid) to C: \ svn_checkout \ P16_RoeV \ Sourcen \ P16Admintool_develop \ P16Common \ CommonMethods.cs: Line 61. At P16Admintool.Helper.InputMaskHelper.UpdateInputMask (InputMasksView designerwindow) to C: \ svn_checkout \ P16_RoeV \ Resources \ P16Admintool_develop \ P16Admintool \ Helper \ InputMaskHelper.cs: Line 39. At P16Admintool.ViewModels.ChangeElementPropertiesViewModel.SetElementProperties () in C: \ svn_checkout \ P16_RoeV \ Sourcen \ P16Admintool_develop \ P16Admintool \ ViewModels \ ChangeElementPropertiesViewModel.cs: Line 152. For P16Admintool.Views.ChangeElementProperties.btn_set_properties_Click (Object sender, RoutedEventArgs e) in C: \ svn_checkout \ P16_RoeV \ Resources \ P16Admintool_develop \ P16Admintool \ Views \ ChangeElementProperties.xaml.cs: Line 77. At System.Windows.RoutedEventHandlerInfo.InvokeHandler (Object target, RoutedEventArgs routedEventArgs) At System.Windows.EventRoute.InvokeHandlersImpl (Object source, RoutedEventArgsArgs, Boolean reRaised) At System.Windows.UIElement.RaiseEventImpl (DependencyObject sender, RoutedEventArgs args) At System.Windows.UIElement.RaiseEvent (RoutedEventArgs e) At System.Windows.Controls.Primitives.ButtonBase.OnClick () At System.Windows.Controls.Button.OnClick () At System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp (MouseButtonEventArgs e) At System.Windows.UIElement.OnMouseLeftButtonUpThunk (Object sender, MouseButtonEventArgs e) At System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler (Delegate genericHandler, Object genericTarget) At System.Windows.RoutedEventArgs.InvokeHandler (Delegate handler, Object target) At System.Windows.RoutedEventHandlerInfo.InvokeHandler (Object target, RoutedEventArgs routedEventArgs) At System.Windows.EventRoute.InvokeHandlersImpl (Object source, RoutedEventArgsArgs, Boolean reRaised) At System.Windows.UIElement.ReRaiseEventAs (DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent) At System.Windows.UIElement.OnMouseUpThunk (Object sender, MouseButtonEventArgs e) At System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler (Delegate genericHandler, Object genericTarget) At System.Windows.RoutedEventArgs.InvokeHandler (Delegate handler, Object target) At System.Windows.RoutedEventHandlerInfo.InvokeHandler (Object target, RoutedEventArgs routedEventArgs) At System.Windows.EventRoute.InvokeHandlersImpl (Object source, RoutedEventArgsArgs, Boolean reRaised) At System.Windows.UIElement.RaiseEventImpl (DependencyObject sender, RoutedEventArgs args) At System.Windows.UIElement.RaiseTrustedEvent (RoutedEventArgs args) At System.Windows.UIElement.RaiseEvent (RoutedEventArgs args, Boolean trusted) At System.Windows.Input.InputManager.ProcessStagingArea () At System.Windows.Input.InputManager.ProcessInput (InputEventArgs input)

It looks like you are missing an eager loading for the related entities. Can you also post the code of the Formulas class to have a look? — Eugene Komisarenko
Hello Eugene. I added the code of the entity Formulas. According to the error message there seems to be a problem with the property of the related entity/table Descriptions. What do You think? — Patrick Pirzer

Eugene Komisarenko Eugene Komisarenko · Accepted Answer · 2017-04-20T13:59:09

Lazy loading and serialization do not mix well, see the following article on why https://msdn.microsoft.com/en-us/library/jj574232(v=vs.113).aspx.

In your case you might need to eagerly load all the dependencies i.e. collections of the following properties. And like you said, it might be a good idea to start with the Descriptions property first.

public virtual Descriptions Descriptions { get; set; }
public virtual ICollection<Formula_Attributes> Formula_Attributes { get; set; }
public virtual ICollection<Formula_Field_Attributes> Formula_Field_Attributes { get; set; }
public virtual ICollection<Input_Field_Formulas> Input_Field_Formulas { get; set; }
public virtual ICollection<Stepfunctions> Stepfunctions { get; set; }

Whenever you call your context to load Formulas you will need to call .Include(..) on the Descriptions and any other lazy loaded collections.

How to serialize an observablecollection of type entity to xml

1 Answers