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POXAML And Dependency Injection
 

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  1. POXAML And Dependency Injection
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    <p>I have a dialog box that is created using MEF and it has an exposed member in its View Model called 'Container' which is a reference to the CompositionContainer. Inside that dialog box is a drop down combobox that has a selection of customers. I want to select a customer from a list that is created from the shared data model. My dialog looks like this:</p> <pre><code>&lt;Window x:Class="MyNamespace.MyDialog" xmlns:common="http://schemas.teraque.com/common" ShowInTaskbar="False" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"&gt; &lt;Grid Margin="4"&gt; &lt;Grid.RowDefinitions&gt; &lt;RowDefinition/&gt; &lt;RowDefinition/&gt; &lt;/Grid.RowDefinitions&gt; &lt;Grid.ColumnDefinitions&gt; &lt;ColumnDefinition /&gt; &lt;ColumnDefinition /&gt; &lt;/Grid.ColumnDefinitions&gt; &lt;common:ProductComboBox Grid.Row="1" Grid.Column="1"/&gt; &lt;TextBlock Text="Product" Grid.Row="0" Grid.Column="0"/&gt; &lt;common:CustomerComboBox Grid.Row="1" Grid.Column="1"/&gt; &lt;TextBlock Text="Customer" Grid.Row="1" Grid.Column="0"/&gt; &lt;/Grid&gt; &lt;/Window&gt; </code></pre> <p>So how do we go about passing along the DI composition container to the Product or Customer combo boxes so they can query the shared services for the product and customer data? I've toyed around with the idea of referencing the container from the parent view model:</p> <pre><code>&lt;common:CustomerComboBox Container="{Binding Container}" Grid.Row="1" Grid.Column="1"/&gt; </code></pre> <p>Is there a better way?</p>
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    1. PTQuestion
    1. USDonald Airey
    1. USDonald Airey
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    1. COUsually passing the composition container around defeats the point of dependency injection. Usually you would be injecting your services into your view models and querying them from there, then binding your combos to properties on the vms that contain the queried values. Passing the container around will just lead to tight coupling and difficult to maintain code
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      1. POXAML And Dependency Injection
      1. USCharleh
    2. COCharleh, how about posting that as an answer so we can vote on it. It looks good. In my mind, I was hoping for some re-usability out of the Customer combobox such that I could just drop the same control into any view and have it work. Your approach suggests that I create a re-usable collection of customers and pull it out of the container in each view model, then make it into a property of each view model that has such a combobox. Not as elegant as just dropping in a CustomerComboBox, but I see how it fits the DI architecture better.
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      1. POXAML And Dependency Injection
      1. USDonald Airey
 

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