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Ticket T747717
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Implementing Basic Drag-Drop Functionality in Master Detail Grid Controls

created 6 years ago

I'm working on a project with several two-level Master Detail gridcontrols using gridviews for both levels. I've been asked to implement drag-drop functionality that allows the users to do the following:

* Reorder rows in the Master gridview.
 * Reorder rows in the Detail gridviews.
 * Move items between Detail gridviews.
 * Move items from a Detail gridview onto an item from the Master gridview, allowing that item to be moved to the end of the Master gridview item's Detail gridview.
 * Move items between a Detail gridview and a completely separate gridview in another gridcontrol.

I've gone over quite a few support articles, and I'm unable to find an example that works properly. I'm able to implement drag-drop functionality at the Master level with relative ease, but I can't seem to get any drag-drop originating from a Detail gridview to work properly no matter what I try. I think, at this point, I need an example project to see how this would be implemented. Can you please either direct me to such example code or create and example for me?

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Answers approved by DevExpress Support

created 6 years ago (modified 6 years ago)

Hi,

The best way to achieve the required functionality is to use DragDropBehaviors. Please note that when you are working in Master-Detail mode, it is necessary to associate DragDropBehavior with a corresponding detail view clone that is created each time you expand a master row.  You can do this by handling the  GridControl.ViewRegistered and GridControl.ViewRemoved events. I created a small sample project to show the main idea of this approach. I hope it will be helpful.
Don't forget that the order of grid rows depends on the sorting applied to GridView. So, to add a capability to reorder grid rows via drag-drop, you should create a separate column to store the current sorting index of each row and implement the custom logic to update this value in the DragDrop event handler.

    Comments (2)
    C C
    Customer41688 6 years ago

      Thank you for the sample project. It took a while, but I was able to figure out what issues were holding me back. For one, I noticed that if you set the "AllowDrop" property to true directly on the gridview, the drag-drop support implemented using the behavior manager will counterintuitively stop working. Also, if you're using custom detail gridviews, the ViewRegistered and ViewRemoved events don't appear to be sufficient. (Although I left them in without any apparent harm.) You have to attach the behavior directly:

      behaviorManager1.Attach<DragDropBehavior>(gridViewCustomDetail);

      Also, you need to make sure that don't have a preexisting Drag-Drop behavior set up in the Designer for your behavior manager for the detail gridviews.

      Well, maybe I'm still doing something wrong, but it works for me. Let me know if you have any comments.

      Sasha (DevExpress Support) 6 years ago

        Hi,

        I am happy to hear that you managed to find a suitable solution.

        You are right, the BehaviorManager functionality is not activated if you enable the standard .NET drag-drop using the AllowDrop property. This behavior is described in the Drag And Drop Behavior help article:
        >>Drag and Drop Behaviors should be attached to the source and target controls to work correctly. Disable the source control's  *AllowDrop setting to allow data to be transferred one way only.

        As for attaching the drag-drop behavior to detail views using the ViewRegistered event, Pavel's example works fine on my side. Please see the attached video. Is it possible to modify it in order to illustrate the issue? It will help us determine its cause.

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