An easy way to refer to DataContext in UserControl View

Hi, Ivan.

As mentioned in the article, we connect View and View Model using the MVVM platform provided by DevExpress and POCO ViewModel and IModuleManager(MIF) to express UserControl by injection into Document Region.

If you use this DevExpress MVVM platform, POCO ViewModel, IModuleManager(MIF), and define DataContext in UserControl will cause an error on the screen, so we are not able to define DataContext like the code you showed us.

Please tell me how to refer to DataContext when using DevExpress MVVM, POCO platform, MIF.

I beg you.

C#
Manager.Register(Regions.Documents, new Module(AppModules.SOLUTION_DIC, () => QsfpSolDictionaryViewModel.Create(AppModules.SOLUTION_DIC, GetSCRN_CD(AppModules.SOLUTION_DIC), LoginViewModel), typeof(QsfpSolDictionaryView)));
Manager.InjectOrNavigate(Regions.Documents, e.NewViewModelKey);

For example

In this case, it is referenced to the DataContext of the dependent object, and to refer to the DataContext of the UserControl View, it is currently required to declare and bind ElementName.

XAML
<dxg:TableView.RowStyle>
    <Style TargetType="{x:Type dxg:RowControl}">
        <Style.Triggers>
            <DataTrigger Value="3" Binding="{Binding Row.ITEM_STATUS}">
                <Setter Property="Background" Value="{Binding DataContext.LN_DEL_TEXT_COLOR,  ElementName="View", UpdateSourceTrigger=PropertyChanged}" />
                <Setter Property="Foreground" Value="{Binding DataContext.LN_DEL_BKGND_COLOR,  ElementName="View", UpdateSourceTrigger=PropertyChanged}" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</dxg:TableView.RowStyle>

Hello,

In your example, you declare a style for rows in GridControl. Rows in GridControl use different DataContexts because they operate with data items and should process information from these items instead. For more information, please refer to this help topic: RowStyle. However, even in this case, you still can use the DataContext that your GridControl inherited from its parent. Each RowControl has a RowData object in their DataContext property. This RowData object contains the View property. This View property references your TableView. Therefore, you can use TableView's DataContext in your binding definitions:

XAML
<dxg:TableView.RowStyle>
    <Style TargetType="{x:Type dxg:RowControl}">
        <Style.Triggers>
            <DataTrigger Value="3" Binding="{Binding Row.ITEM_STATUS}">
                <Setter Property="Background" Value="{Binding View.DataContext.LN_DEL_TEXT_COLOR}" />
                <Setter Property="Foreground" Value="{Binding View.DataContext.LN_DEL_BKGND_COLOR}" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</dxg:TableView.RowStyle>

I recommend using tools similar to Snoop to review the visual tree and data context of target elements at runtime. This will help you build correct binding paths.

Let me know if you have other questions.

Thanks,
Andrey

Hello

Your answer is completely different from the gist of the question I asked. I already know that you refer to DataContext in TableView when you perform Binding on RowControl.

I'm not curious about this, but I'd like to refer to the DataContext of UserControl.

For this purpose, UserControl View is assigned a Name, which is referenced by RowControl using DataContext and ElementName.

However, because our project uses MIF modules provided by DevExpress, we do not inherit DataContext directly from the UserControl View group, but use ModuleManger in MainView to connect View and ViewModel through Injection.

In this case, I am asking you how to refer to DataContext in UserControl.

Summary:

1. The goal is to set the row color using RowControl in the Table VIEW Style in UserControl.
2. DataContext referenced by RonControl is DataContext in TableView, so set the name in UserControl and refer to UserControl DataContext under the ElementName condition.
3. I want to know how to refer to DataContext in UserControl View without ElementName.
4. Due to the use of MIF modules, inheriting DataContext from UserControl from xaml to a specific variable as described by Ivam in the above article causes a problem (because ViewModel already connected through ModuleManager)

That's why I asked if there is a dxci, dvvm method that refers to DataContext in UserControl.

Please take a look at the code example written above and give us a proper answer again.

Add.

In Andrey's example code,

XAML
Value="{Binding View.DataContext.LN_DEL_TEXT_COLOR}"

The 'View' in this part is…

XAML
<UserControl DataContext="View">

Does it apply when you declare?

Hello,

We don't have special properties for this scenario. You can either use standard binding types (e.g., different RelativeSource binding definitions) or implement a custom attached property if this is essential in your scenario.

As for MIF, this does not really relate to the question that we are discussing. In this framework, we only set DataContext and do not affect the default inheritance mechanism of this property. All techniques that work in WPF in general will work in applications based on MIF.

Regarding my binding configuration ({Binding View.DataContext.LN_DEL_TEXT_COLOR}), RowControl does not inherit DataContext from the parent TableView/GridControl, as I mentioned previously. RowControl contains RowData in its DataContext. In this particular scenario, you can get access to the DataContext object inherited from the parent container of GridControl via the TableView's DataContext. The View property in the RowData object contains the view that GridControl contains in its View property. It's not the UserControl with the 'View' name that you mentioned. But this solution still allows you to get DataContext from this parent UserControl if GridControl inherits this DataContext object in your layout.

Thanks,
Andrey

Hi, Andery.

The one you suggested.

XAML
Value="{Binding View.DataContext.LN_DEL_TEXT_COLOR}"

We've solved the problem.
This was the way to refer to DataContext in the View without using ElementName.

Thank you very much! :)

By the way, I have a question.

In our project, we use MIF and connect View and ViewModel through MIF Register and Inject, but contrary to your words, inheriting DataContext as a specific variable in UserControl causes problems.

It seems that there is a new DataContext inherited from View, not a ViewModel connected to the MIF when the injection is made. So the data from ViewModel connected to the MIF can't bind at all.

Am I doing something wrong? Can you tell me an example or method of inheriting DataContext from UserControl?

Hello,

I'm happy to hear that the issue with getting the data context at the row level is now resolved. Thank you for keeping us informed.

As for the issue with the DataContext in applications created with MIF, I created a new application and checked data context in elements from the view. As you can see in the project and screencast that I attached below, data context is correctly inherited by child elements from the parent UserControl (view). In my research I used the Snoop tool. As I described above, this tool allows you to check data context at runtime. I recommend that you try this tool to research data context in problematic elements. This can help you find the cause of issues and find a solution. Should you face difficulties with this, please update my project to illustrate the same problematic behavior. I hope to hear from you soon.

Thanks,
Andrey