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.netwpfmvvmdrag-and-drop

How to handle drag/drop without violating MVVM principals?

Currently I have in my XAML

<TabControl  
    AllowDrop="True"
    PreviewDragOver="DragOver"
    PreviewDrop="Drop" />

All of my drag/drop code exists within the codebehind of my View, rather than within my ViewModel.

How can I handle drag/drop in my ViewModel without adding any dependencies on the View?

Solution

  • There are libraries for this such as gong and similar snippets on various blog articles.

    However, you shouldn't get too hung up on having absolutely no code-behind. For example, this is still MVVM in my book:

    void ButtonClicked(object sender, EventArgs e)
{
    ((MyViewModel) this.DataContext).DoSomething();
}

    A command binding might be a better choice, but the logic is definitely in the viewmodel. With something like Drag and Drop, it's more variable where you want to draw the line. You can have code-behind interpret the Drag Args and call methods on the viewmodel when appropriate.