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POValidating bound ObservableCollection in ViewModel using MVVM Pattern
 

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    <p>I'm new to MVVM, just recently started my first project following the MVVM pattern. I have an issue trying to validate an ObservableCollection using the IDataErrorInfo Interface. My ObservableCollection looks like this:</p> <pre><code>ObservableCollection&lt;Magazine&gt; magazineRepository; public ObservableCollection&lt;Magazine&gt; MagazineRepository { get { return magazineRepository; } set { if (value != null) { bladRepository = value; OnPropertyChanged("MagazineRepository"); } } } </code></pre> <p>And my XAML like this:</p> <pre><code>&lt;ListBox x:Name="listMagazineRepository" Grid.ColumnSpan="2" ItemsSource="{Binding}" DataContext="{Binding MagazineRepository}" DisplayMemberPath="Navn" SelectedItem="{Binding Path=SelectedItem}"/&gt; &lt;TextBox x:Name="txtName" Grid.Row="1" Grid.Column="0" Text="{Binding ElementName=listMagazineRepository, Path=SelectedItem.Navn, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" /&gt; &lt;TextBox x:Name="txtPrice" Grid.Row="2" Grid.Column="0" Text="{Binding ElementName=listMagazineRepository, Path=SelectedItem.Pris, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" /&gt; </code></pre> <p>It's just a simple listBox containing objects, when you select an item, the selected objects properties is displayed in the textboxes, and is then bound to the listbox object.</p> <p>My Problem is, that when I set my code up like this, the only way I can figure out how to validate my data is in the Domain Model, which really isn't a good practise, I'd like to validate in the ViewModel before it gets there. Basically I want to validate each property in the MagazineRepository, in the ViewModel, How would you go about doing this?</p> <p>PS: I'm new to posting on this board (and programming boards in general) if my question is lacking information, please let me know and I will supply the needed details. </p> <p>Thanks a lot. </p>
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    1. COWell I don't see a ViewModel in your code that you posted, but the typical way would be for your ViewModel to implement IDataErrorInfo
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    2. COSorry, I thought it was implied. The collection is in my ViewModel, which indeed does implement IDataErrorInfo, but when the textbox change a property in the collection, I need to validate on that property and I can't figure out how exactly to do that. So there's 2 textboxes each is bound to a property in the collection, and when that property change I need to do validation on it, doing it the way I learned with IDataErrorInfo I can only validate the whole collection.
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