Скачать или смотреть How to Effectively Share a DataContext for Two UserControls in WPF MVVM

Learn how to manage a shared `DataContext` between two UserControls in WPF MVVM by using enum to distinguish between different views, ensuring organized and effective code.
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This video is based on the question https://stackoverflow.com/q/70448797/ asked by the user 'JJNL77' ( https://stackoverflow.com/u/9033837/ ) and on the answer https://stackoverflow.com/a/70460196/ provided by the user 'DungNH' ( https://stackoverflow.com/u/5966343/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing Shared DataContext in WPF MVVM with UserControls

In the world of WPF (Windows Presentation Foundation) and MVVM (Model-View-ViewModel) architecture, developers often encounter scenarios where multiple UserControls need to share the same data context. This can become particularly challenging when each UserControl needs to behave differently based on its specific type, such as an Audi versus a BMW. So, how can we effectively manage this situation? In this post, we will walk through a simple solution to enable both UserControls to utilize the same ViewModel while ensuring that they behave according to their unique requirements.

The Problem

You have two UserControls, Audi.xaml and Bmw.xaml, that require the same ViewModel (BrandViewModel). However, you want to invoke different functions based on which UserControl is currently in use. This creates a need to differentiate between the two UserControls within the ViewModel, leading to distinct actions when methods are called related to Audi or BMW.

Specific Requirements:

Maintain a cohesive data context across both UserControls.

Dynamically invoke specific methods based on the UserControl being used.

The Solution

To tackle this problem, we will implement an enum to define the brand type associated with each UserControl. Then, we will modify the ViewModel to accept this information during instantiation.

Step 1: Create an Enum

First, we will create an enum called Brands that will represent the different car brands. This allows for clear, type-safe identification of which UserControl is used.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Modify the ViewModel’s Constructor

Next, we will alter the BrandViewModel to accept the Brands enum as a parameter. This will help us assign the correct brand context within the ViewModel.

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Update UserControl Constructors

Now that the ViewModel can determine its brand, we need to ensure each UserControl passes its brand type when instantiating the ViewModel. Here’s how to modify the constructors for Audi.xaml.cs and Bmw.xaml.cs:

For Audi.xaml.cs:

[[See Video to Reveal this Text or Code Snippet]]

For Bmw.xaml.cs:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing an enum for brand types and modifying the ViewModel to accept this information, we can easily manage and utilize shared DataContext between multiple UserControls in WPF MVVM. This approach not only keeps your code clean and organized but also allows for greater flexibility and adaptability in your application’s design.

Now you can seamlessly add more UserControls in the future by simply extending the Brands enum, making your application scalable and maintainable. Happy coding!