How to define the usercontrols in mvvm pattern?

Question

I using from mvvm in my application. I want know how to define my user control in mvvm pattern.

Must I define it by using from mvvm, or I can define it generally?

Answer 1

Let's just call the control that embeds the user control MainWindow, and the user control UserControl. Since you are in MVVM pattern, you have at least one View Model for the outer view - I usually use the name MainVm. You have two choices for the user control: They can share the same View Model, or you could have a sub view model, just for the UserControl, i.e. UserVm.

For your first choice, you do nothing. You define UserControl (Visual Studio 'add new item' -> User Control is a pretty good start). Then, you simply embed it in Main Window.

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UserControl will inherit the same DataContext from MainWindow, and do all the {Binding} as you would do in the MainWindow.

If you want to have a sub view model (UserVm) - it would typically be a public property of the MainVm (say, userVm). In that case, you'll set the DataContext of the UserControl when you reference it.

Another popular paradigm would be to declare the DataTemplate instead of the UserControl. If you do that, you just need to put the UserVm (either instantiate it in the XAML, or through binding):

    
           
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