Drag and Drop in EJ 1 ASP.NET MVC TreeView

16 Aug 2018 / 10 minutes to read

To perform drag and drop operation in TreeView specify AllowDragAndDrop as true. It allows you to drag and drop node in all level of same TreeView.
The nodeDrag, nodeDragStart, nodeDragStop and
nodeDropped event occurs based on Treeview node drag and drop state.

  • razor
  • @(Html.EJ().TreeView("treeView")
            .TreeViewFields(field =>
                field.Datasource((IEnumerable<LoadData>)ViewBag.datasource)
                .Id("Id")
                .ParentId("Parent")
                .Text("Text")
            )
            .AllowDragAndDrop(true)
        )

    NOTE

    TreeView provides much easier option to drop the dragged nodes at any levels by indicator lines with icons.

    Position Indicators

    TreeView provides much easier option to drop the dragged nodes at any levels by indicator lines with icons such as line, plus/ minus and restrict icons while dragging and dropping the nodes. It represents exact position where the node to be dropped as sibling or child.

    Indicators

    description

    Plus icon represents the dragged node to be added as child of targeted node
    Minus with restrict icon represents the dragged node not to be dropped at the hovered region
    In between icon represents the dragged node to be dropped in between the nodes as siblings

    Restriction

    You can restrict the dragged nodes to be dropped at siblings or children’s level by using AllowDropSibling and AllowDropChild properties.

  • razor
  • @(Html.EJ().TreeView("treeView")
            .TreeViewFields(field =>
                field.Datasource((IEnumerable<LoadData>)ViewBag.datasource)
                .Id("Id")
                .ParentId("Parent")
                .Text("Text")
            )
            .AllowDragAndDrop(true)
            .AllowDropSibling(true)
            .AllowDropChild(false)
        )

    Drag and drop between Trees

    You can drag and drop tree nodes between two TreeView by setting AllowDragAndDrop as true along with AllowDragAndDropAcrossControl as true.

    In the controller page, create a data list that contains the details about tree nodes.

  • c#
  • public partial class TreeViewController : Controller
            {
                List<LoadData> tree1 = new List<LoadData>();
                List<LoadData> tree2 = new List<LoadData>();
                public ActionResult TreeViewFeatures()
                {
                    tree1.Add(new LoadData { Id = 1, Parent = 0, Text = "Item 1" });
                    tree1.Add(new LoadData { Id = 2, Parent = 0, Text = "Item 2" });
                    tree1.Add(new LoadData { Id = 3, Parent = 0, Text = "Item 3" });
                    tree1.Add(new LoadData { Id = 4, Parent = 0, Text = "Item 4" });
                    tree1.Add(new LoadData { Id = 5, Parent = 1, Text = "Item 1.1" });
                    tree1.Add(new LoadData { Id = 6, Parent = 1, Text = "Item 1.2" });
                    tree1.Add(new LoadData { Id = 7, Parent = 1, Text = "Item 1.3" });
                    tree1.Add(new LoadData { Id = 8, Parent = 3, Text = "Item 3.1" });
                    tree1.Add(new LoadData { Id = 9, Parent = 3, Text = "Item 3.2" });
                    tree1.Add(new LoadData { Id = 10, Parent = 5, Text = "Item 1.1.1" });
                    ViewBag.datasource1 = tree1;
        
                    tree2.Add(new LoadData { Id = 11, Parent = 0, Text = "Item 5" });
                    tree2.Add(new LoadData { Id = 12, Parent = 0, Text = "Item 6" });
                    tree2.Add(new LoadData { Id = 13, Parent = 0, Text = "Item 7" });
                    tree2.Add(new LoadData { Id = 14, Parent = 0, Text = "Item 4" });
                    tree2.Add(new LoadData { Id = 15, Parent = 11, Text = "Item 5.1" });
                    tree2.Add(new LoadData { Id = 16, Parent = 11, Text = "Item 5.2" });
                    tree2.Add(new LoadData { Id = 17, Parent = 11, Text = "Item 5.3" });
                    tree2.Add(new LoadData { Id = 18, Parent = 13, Text = "Item 7.1" });
                    tree2.Add(new LoadData { Id = 19, Parent = 13, Text = "Item 7.2" });
                    tree2.Add(new LoadData { Id = 10, Parent = 15, Text = "Item 5.1.1" });
                    ViewBag.datasource2 = tree2;
                    return View();
                }
            }

    In the view page, add TreeView helper and map the properties defined in to the corresponding fields in data source and specify the drag and drop settings.

  • razor
  • @(Html.EJ().TreeView("treeViewDrag")
            .TreeViewFields(field =>
                field.Datasource((IEnumerable<LoadData>)ViewBag.datasource1)
                .Id("Id")
                .ParentId("Parent")
                .Text("Text")
            )
            .AllowDragAndDrop(true)
            .AllowDropSibling(true)
            .AllowDropChild(true)
            .AllowDragAndDropAcrossControl(true)
        )
        <br />
        <br />
        @(Html.EJ().TreeView("treeViewDrop")
            .TreeViewFields(field =>
                field.Datasource((IEnumerable<LoadData>)ViewBag.datasource2)
                .Id("Id")
                .ParentId("Parent")
                .Text("Text")
            )
            .AllowDragAndDrop(true)
            .AllowDropSibling(true)
            .AllowDropChild(true)
            .AllowDragAndDropAcrossControl(true)
        )

    Auto node structuring

    You may not need to have two TreeView to be in same structured node while drag and drop the nodes between them. But after the node has been dropped, it should get structure of the TreeView node in which dropped. By default TreeView auto structure the node whenever you drop a node from different tree.

  • razor
  • @(Html.EJ().TreeView("treeViewDrag")
            .TreeViewFields(field =>
                field.Datasource((IEnumerable<LoadData>)ViewBag.datasource1)
                .Id("Id")
                .ParentId("Parent")
                .Text("Text")
            )
            .AllowDragAndDrop(true)
            .AllowDropSibling(true)
            .AllowDropChild(true)
            .AllowDragAndDropAcrossControl(true)
            .ShowCheckbox(true)
        )
        <br />
        <br />
        @(Html.EJ().TreeView("treeViewDrop")
            .TreeViewFields(field =>
                field.Datasource((IEnumerable<LoadData>)ViewBag.datasource2)
                .Id("Id")
                .ParentId("Parent")
                .Text("Text")
            )
            .AllowDragAndDrop(true)
            .AllowDropSibling(true)
            .AllowDropChild(true)
            .AllowDragAndDropAcrossControl(true)
        )

    NOTE

    Auto node structure only applicable for well-structured node object.