Node Interaction in Blazor Diagram Component

30 Jun 202511 minutes to read

Diagram provides the support to select, drag, resize, or rotate the node interactively.

How to Select a Node

A node can be selected at runtime by using the Select method and the selection can be cleared by using the ClearSelection method. The following code explains how to select and clear the selection in the diagram.

@using Syncfusion.Blazor.Diagram
@using System.Collections.ObjectModel
@using Syncfusion.Blazor.Buttons


<SfButton Content="Select" OnClick="@OnSelect" />
<SfButton Content="UnSelect" OnClick="@UnSelect" />
<SfDiagramComponent @ref="@diagram" Height="600px" Nodes="@nodes" />

@code
{
    // Reference of the diagram
    SfDiagramComponent diagram;
    // To define node collection
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        // A node is created and stored in nodes collection.
        Node node = new Node()
            {
                // Position of the node
                OffsetX = 250,
                OffsetY = 250,
                // Size of the node
                Width = 100,
                Height = 100,
                Style = new ShapeStyle() { Fill = "#6495ED", StrokeColor = "white" }
            };
        // Add node
        nodes.Add(node);
    }

    public void OnSelect()
    {
        // Select the node
        diagram.Select(new ObservableCollection<IDiagramObject> { diagram.Nodes[0] });
    }

    public void UnSelect()
    {
        // clear selection in the diagram
        diagram.ClearSelection();
    }
}

You can download a complete working sample from GitHub

And also the selection enable during the interaction.

  • An element can be selected by clicking that element.
  • When you select the elements in the diagram, the SelectionChanging and SelectionChanged events get triggered and do customization on those events.

Node Selection in Blazor Diagram

How to Drag a Node

A node can be dragged at runtime by using the Drag method. The following code explains how to drag the node by using the drag method.

@using Syncfusion.Blazor.Diagram
@using Syncfusion.Blazor.Buttons


<SfButton Content="Drag" OnClick="@OnDrag" />
<SfDiagramComponent @ref="@Diagram" Height="600px" Nodes="@nodes" />

@code
{
    // Reference of the diagram
    SfDiagramComponent Diagram;
    // To define node collection
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        // A node is created and stored in nodes collection.
        Node node = new Node()
            {
                // Position of the node
                OffsetX = 250,
                OffsetY = 250,
                // Size of the node
                Width = 100,
                Height = 100,
                Style = new ShapeStyle() { Fill = "#6495ED", StrokeColor = "white" }
            };
        // Add node
        nodes.Add(node);
    }

    public void OnDrag()
    {
        // Drag the node
        Diagram.Drag(Diagram.Nodes[0], 10, 10);
    }
}

You can download a complete working sample from GitHub

Also, drag the node during the interaction.

  • An object can be dragged by clicking and dragging it. When multiple elements are selected, dragging any one of the selected elements moves all the selected elements.
  • When you drag the elements in the diagram, the PositionChanging and PositionChanged events get triggered and do customization on those events.

Dragging Node at Runtime in Blazor Diagram

How to Resize a Node

A node can be resized at runtime by using the Scale method. The following code explains how to resize the node by using the scale method.

@using Syncfusion.Blazor.Diagram
@using Syncfusion.Blazor.Buttons


<SfButton Content="Resize" OnClick="@OnResize" />
<SfDiagramComponent @ref="@diagram" Height="600px" Nodes="@nodes" />

@code
{
    // Reference of the diagram
    SfDiagramComponent diagram;
    // To define node collection
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        // A node is created and stored in nodes collection.
        Node node = new Node()
            {
                // Position of the node
                OffsetX = 250,
                OffsetY = 250,
                // Size of the node
                Width = 100,
                Height = 100,
                Style = new ShapeStyle() { Fill = "#6495ED", StrokeColor = "white" }
            };
        // Add node
        nodes.Add(node);
    }

    public void OnResize()
    {
        // Resize the node
        diagram.Scale(diagram.Nodes[0], 0.5, 0.5, new DiagramPoint() { X = 0, Y = 0 });
    }
}

You can download a complete working sample from GitHub

Also, you can resize the node during interaction.

  • Selector is surrounded by eight thumbs. When dragging these thumbs, the selected items can be resized.
  • When one corner of the selector is dragged, the opposite corner will be in a static position.
  • When a node is resized, the SizeChanging and SizeChanged events get triggered.

Node Resizing in Blazor Diagram

How to Rotate a Node

A node can be rotated at runtime by using the Rotate method. The following code explains how to rotate the node by using the rotate method.

@using Syncfusion.Blazor.Diagram
@using Syncfusion.Blazor.Buttons


<SfButton Content="Rotate" OnClick="@OnRotate" />
<SfDiagramComponent @ref="@diagram" Height="600px" Nodes="@nodes" />

@code
{
    // Reference of the diagram
    SfDiagramComponent diagram;
    // To define node collection
    DiagramObjectCollection<Node> nodes;

    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        // A node is created and stored in nodes collection.
        Node node = new Node()
        {
            // Position of the node
            OffsetX = 250,
            OffsetY = 250,
            // Size of the node
            Width = 100,
            Height = 100,
            Style = new ShapeStyle() { Fill = "#6495ED", StrokeColor = "white" }
        };
        // Add node
        nodes.Add(node);
    }

    public void OnRotate()
    {
        // Rotate the node
        diagram.Rotate(diagram.Nodes[0], diagram.Nodes[0].RotationAngle + 10);
    }
}

You can download a complete working sample from GitHub

Also, rotate the node during the interaction.

  • A rotate handler is placed above the selector. Clicking and dragging the handler in a circular direction leads to rotating the node.
  • The node is rotated with reference to the static pivot point.
  • Pivot thumb (thumb at the middle of the node) appears when rotating the node to represent the static point.
  • When a node is rotated, the RotationChanging and RotationChanged events get triggered.

Displaying Node Rotation in Blazor Diagram

How to rotate a node using the RotationAngle property

The RotationAngle property gets or sets the rotation angle of a node in degrees. This defines the fixed angle at which the node is displayed. The default value is 0.

Use this property when you want to specify the node’s rotation at the time of creation or update it programmatically.

@using Syncfusion.Blazor.Diagram
<SfDiagramComponent Height="600px" Nodes="@nodes" />
@code
{
    DiagramObjectCollection<Node> nodes = new DiagramObjectCollection<Node>();
    protected override void OnInitialized()
    {
        Node node = new Node()
        {
            ID = "node1",
            Height = 100,
            Width = 100,
            OffsetX = 100,
            OffsetY = 100,
            RotationAngle = 50, // Rotates node by 50 degrees
        };
        nodes.Add(node);
    }
}

You can download a complete working sample from GitHub

Node Resizing in Blazor Diagram

How to Flip a Node

The Flip is performed to give the mirrored image of the original element.

For more information about node flip, refer to Node Flip.

See also