Using Unity in WPF Custom Controls

Question

I'm attempting to create a WPF custom control that includes a reference to the unity container that has been created in the BootStrapper - e.g.

The reason being that I would like the custom control to be able to resolve the unity container to be able to use some of the services that have been registered to the container. e.g. a user preference service / an entitlements service.

So far I have created my custom control and have included in the code behind file the following dependency property

public static readonly DependencyProperty ContainerProperty = DependencyProperty.Register("Container", typeof(UnityContainer), typeof(SomeCustomWPFControl), new PropertyMetadata("DefaultTestValue"));

    public UnityContainer Container
    {
        get { return (UnityContainer)GetValue(ContainerProperty); }
        set { SetValue(ContainerProperty, value); }
    }

In the WPF form where I'm attempting to include my custom control, I've added the following line to the Resources area:

<Unity:UnityContainer x:Key="unitContainer"></Unity:UnityContainer>

In the form it's self I've attempted to create the custom control:

<Globe:SomeCustomWPFControl Container="{DynamicResource unitContainer}" DockPanel.Dock="Right" x:Name="JimEditor1" Grid.Column="0" Grid.Row="3"></Globe:SomeCustomWPFControl>

The only error information I receive at run time is

Error at object 'System.Windows.Controls.Grid' in markup file '[assembly name];[path/file].xaml' Line 135 Position 22.

Any suggestions as to where I'm going wrong? Thx.

Full Xaml:

<UserControl x:Class="DB.GPF.Globe.Views.JimTestPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
xmlns:Globe="clr-namespace:DB.GPF.Globe" 
xmlns:Unity="clr-namespace:Microsoft.Practices.Unity;assembly=Microsoft.Practices.Unity">
<UserControl.Resources>
    <Unity:UnityContainer x:Key="unitContainer"></Unity:UnityContainer>
</UserControl.Resources>
<Grid>
    <Globe:SomeCustomWPFControl Container="{DynamicResource unitContainer}" x:Name="JImTestControl1"></Globe:SomeCustomWPFControl>
</Grid>

Update: The problem appears to be having a DependencyProperty of type UnityContainer or IUnityContainer, if the type is changed to an inbuilt .Net type, e.g. string then it runs fine. Any ideas why we can't have a DependencyProperty of type UnityContainer or IUnityContainer?

Can you post the rest of your Xaml?

Dan Puzey
– Dan Puzey

2010-10-13 13:35:47 +00:00
Commented Oct 13, 2010 at 13:35 — Dan Puzey
– Dan Puzey, Commented Oct 13, 2010 at 13:35
Here's the Xaml in full:

Jim
– Jim

2010-10-13 15:09:17 +00:00
Commented Oct 13, 2010 at 15:09 — Jim
– Jim, Commented Oct 13, 2010 at 15:09

TalentTuner · Accepted Answer · 2010-10-13 13:37:33Z

1

I think , embedding Unity in Custom Control is not a good idea.

If you need to change some properties of your custome control than expose those properties and change them

answered Oct 13, 2010 at 13:37

TalentTuner

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7 Comments

Jim Over a year ago

The idea is that during the control creation, it will use the services to get hold of the preferences and entitlements that apply to that control. I.e. if it shows date in UK/US format, if the current user can adit that control. etc...

TalentTuner Over a year ago

Can't you change these properties without embedding unity in your code? Why i am saying this becoz if yoy embedd unity in your control , your control itself depend upon the unity and if in future , you need to replace unity with someother DI provider than you will change your Custom Control which i think is not a good advice, rest it's your code , you can do what you want to do in it :)

RonaldV Over a year ago

saurabh is right. You shouldn't add a container to your code. I would always recommend against it. The container should inject the objects and values into your control.

Jim Over a year ago

Thanks for your responses guys but I don't understand your objections to this at the moment. The idea of using unity is to allow for the changing of the service implementations I'm making use of in the future in true IoC style.

Dan J Over a year ago

@Jim I believe the objections arise from the fact that you're replacing a dependency on a given service implementation with a dependency on the container itself. Better practice would be to have your custom control accept an IPreferenceServer, for example, and use the Unity container outside the control to resolve an IPreferenceServer implementation and then inject the service into the control.

|

RonaldV · Accepted Answer · 2010-10-13 14:25:53Z

0

<Globe:SomeCustomWPFControlContainer="{DynamicResource unitContainer}" DockPanel.Dock="Right" x:Name="JimEditor1" Grid.Column="0" Grid.Row="3"></Globe:SomeCustomWPFControlContainer>

There is a problem in you xaml right after <Globe:SomeCustomWPFControlContainer. You're missing a property to bind to.

EDIT: your get value is also wrong. You have GetValue(GetValue(ContextMenuProperty)) and it should be ...

public UnityContainer Container
{
    get { return (UnityContainer)GetValue(ContainerProperty); }
    set { SetValue(ContainerProperty, value); }
}

edited Oct 13, 2010 at 14:25

answered Oct 13, 2010 at 13:33

RonaldV

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2 Comments

Jim Over a year ago

<Globe:SomeCustomWPFControl Container="{DynamicResource unitContainer}" DockPanel.Dock="Right" x:Name="JimEditor1" Grid.Column="0" Grid.Row="3"></Globe:SomeCustomWPFControl>

Jim Over a year ago

Thanks for the quick responses, you are of course correct, I've changed this in my code, but it's had no effect as I'm presuming it fails before the getter is used. I'm presuming the error is down to the run time not being able to find my unity controller, but can't figure out how to include this correctly in the resource area.

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