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POHierarchicalDataTemplate and Many-To-Many with Payload Entities Navigation Binding Issue
 

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  1. POHierarchicalDataTemplate and Many-To-Many with Payload Entities Navigation Binding Issue
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    <p>I have two Many-To-Many with Payload entities as shown below: </p> <p><img src="https://i.stack.imgur.com/X3lFS.png" alt="Entity Snapshot"></p> <p>So, to make an <strong>Assembly</strong> stored in MasterPartNumber with a part number: <code>MasterPartNumber.pn</code>, I use the navigation property <code>ParentBOMs</code>, which is given by the relationship: <code>MasterPartNumber.pnID = MasterPartsList.parentPnID</code>. This gives me all the child pnIDs under that parent assembly. </p> <p>To get the <strong>child part numbers for that assembly</strong>, I use the <code>ChildPn</code> navigation property, defined by <code>MasterPartsList.pnID = MasterPartNumber.pnID</code>. </p> <p>Please note that top level assembly items are NOT listed in MasterPartsList (they would have a parentPnID that is null).</p> <p>My TreeView HierarchicalDataTemplate binding is:</p> <pre><code>&lt;TreeView x:Name="AssemblyTreeView" ItemsSource="{Binding BOMItems}"&gt; &lt;TreeView.ItemTemplate&gt; &lt;HierarchicalDataTemplate DataType="{x:Type local:MasterPartNumber}" ItemsSource="{Binding ParentBOMs.ChildPn}"&gt; &lt;TextBlock Text="{Binding pn}" /&gt; &lt;/HierarchicalDataTemplate&gt; &lt;/TreeView.ItemTemplate&gt; &lt;/TreeView&gt; </code></pre> <p>Which I believe to be correct. I can step through the debugger and see that the entire BOMItem navigation properties are populated (ParentBOM.ChildPn.pn) for each item that has child information.</p> <p>WHY am I unable to see these child properties populated in my TreeView?!</p> <pre><code>What I should get: Root Assembly --Sub Assembly ----Sub Assembly ------Child (n-levels deep) </code></pre> <p>And</p> <p>What I actually get:</p> <pre><code>Root Assembly </code></pre> <p>Do I need an additional converter? Do I need to define my ObservableCollection object wrapper's "getter" further?</p> <pre><code>Known possible sources of the problem: 1. Entity Framework is lazy loading, and just hasn't loaded the navigation properties I see in the debugger being populated. (No, set LazyLoading to false.) 2. My HierarchicalDataTemplate isn't probing for children just on the fact that it has children -- aka it only understands to switch the binding path when a new DataType is available, or something like that. (Not likely, because I've seen HierarchcialDataTemplates for self-referencing entities of a single entity type.) What I have right: 1. I can cascade down the binding route I told my TreeView to take in the debugger. Parent `pn` is populated as well as its `ParentBOMs.ChildPn.pn`. </code></pre> <p>Please help! Thank you !</p>
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