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Context Menu in ASP.NET Core Diagram control

In graphical user interface (GUI), a context menu is a type of menu that appears when you perform right-click operation. Nested level of context menu items can be created. Diagram provides some in-built context menu items and allows to define custom menu items through the contextMenuSettings property.

Customize context menu

The show property helps you to enable/disable the context menu. Diagram provides some default context menu items to ease the execution of some frequently used commands. The following code illustrates how to enable the default context menu items.

tagHelper
default.cs
<ejs-diagram id="container" width="100%" height="700px" connectors="@ViewBag.connectors" nodes="@ViewBag.nodes">
<e-diagram-contextmenusettings show="true"></e-diagram-contextmenusettings>
</ejs-diagram>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Syncfusion.EJ2.Diagrams;
using System.Drawing;

namespace EJ2MVCSampleBrowser.Controllers.Diagram {
    public partial class DiagramController: Controller {
        // GET: Nodes
        public ActionResult Nodes() {

            List < DiagramNode > nodes = new List < DiagramNode > ();
            List < DiagramNodeAnnotation > Node1 = new List < DiagramNodeAnnotation > ();
            Node1.Add(new DiagramNodeAnnotation() {
                Content = "node1", Style = new DiagramTextStyle() {
                    Color = "White", StrokeColor = "None"
                }
            });
            List < DiagramNodeAnnotation > Node2 = new List < DiagramNodeAnnotation > ();
            Node2.Add(new DiagramNodeAnnotation() {
                Content = "node2", Style = new DiagramTextStyle() {
                    Color = "White", StrokeColor = "None"
                }
            });
            nodes.Add(new DiagramNode() {
                Id = "node1",
                    Width = 100,
                    Height = 100,
                    Style = new NodeStyleNodes() {
                        Fill = "darkcyan"
                    },
                    OffsetX = 100,
                    OffsetY = 100,
                    Annotations = Node1
            });
           nodes.Add(new DiagramNode() {
                Id = "node2",
                    Width = 100,
                    Height = 100,
                    Style = new NodeStyleNodes() {
                        Fill = "darkcyan"
                    },
                    OffsetX = 300,
                    OffsetY = 300,
                    Annotations = Node2
            });
            ViewBag.nodes = nodes;

            List<DiagramConnector> Connectors = new List<DiagramConnector>();
            Connectors.Add(new DiagramConnector() { Id = "connector", SourcePoint = new DiagramPoint() { X = 100, Y = 100 }, TargetPoint = new DiagramPoint() { X = 300, Y = 300 }  });
            ViewBag.connectors = Connectors;


            return View();
        }
    }
}

Context menu can be defined for individual node with the desired context menu items.

  • Apart from the default context menu items, define some additional context menu items. Those additional items have to be defined and added to the items property of the context menu.
  • Set text and ID for context menu item using the context menu text and ID properties respectively.
  • Set an image for the context menu item using the context menu url property.
  • The iconCss property defines the class/multiple classes separated by a space for the menu item that is used to include an icon. Menu item can include font icon and sprite image.
  • The target property used to set the target to show the menu item.
  • The separator property defines the horizontal lines that are used to separate the menu items. You cannot select the separators. You can enable separators to group the menu items using the separator property.

The following code example illustrates how to add custom context menu items.

tagHelper
item.cs
<ejs-diagram id="container" width="100%" height="700px" connectors="@ViewBag.connectors" nodes="@ViewBag.nodes">
<e-diagram-contextmenusettings show="true" showCustomMenuOnly="false" items="@ViewBag.item" ></e-diagram-contextmenusettings>
</ejs-diagram>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Syncfusion.EJ2.Diagrams;
using System.ComponentModel;
using Syncfusion.EJ2;
using Newtonsoft.Json;

namespace sample1.Controllers
{
    public class NodeController: Controller
    {
        // GET: Node
        public ActionResult Node()
        {
            // Sets the Annotation for the Node
            List<DiagramNode> Nodes = new List<DiagramNode>();
          
            List<DiagramNodeAnnotation> Node1 = new List<DiagramNodeAnnotation>();
            Node1.Add(new DiagramNodeAnnotation()
            {
                //Sets the offset for the content
                Content = "Node1",
                Hyperlink = new { link = "" },
                Style = new DiagramTextStyle()
                {
                    Color = "black",
                    Fill = "transparent"
                },
                //Sets the margin for the annotation
                Margin = new DiagramMargin() { Top = 10 },
                // Sets the horizontal alignment as left
                HorizontalAlignment = Syncfusion.EJ2.Diagrams.HorizontalAlignment.Left,
                // Sets the vertical alignment as Center
                VerticalAlignment = Syncfusion.EJ2.Diagrams.VerticalAlignment.Center
            });
            List<DiagramNodeAnnotation> Node2 = new List<DiagramNodeAnnotation>();
            Node2.Add(new DiagramNodeAnnotation()
            {
                //Sets the offset for the content
                Content = "Node1",
                Style = new DiagramTextStyle()
                {
                    Color = "black",
                    Fill = "transparent"
                },
                //Sets the margin for the annotation
                Margin = new DiagramMargin() { Bottom = 10 },
                // Sets the horizontal alignment as left
                HorizontalAlignment = Syncfusion.EJ2.Diagrams.HorizontalAlignment.Left,
                // Sets the vertical alignment as Center
                VerticalAlignment = Syncfusion.EJ2.Diagrams.VerticalAlignment.Center
            });
            Nodes.Add(new DefaultNode()
            {
                Id = "Node1",
                OffsetY = 100,
                OffsetX = 100,
                Height = 100,
                Width = 100,
                // add the Annotation for the Node
                Annotations = Node1,
            });
            Nodes.Add(new DefaultNode()
            {
                Id = "Node2",
                OffsetY = 100,
                OffsetX = 100,
                Height = 100,
                Width = 100,
                // add the Annotation for the Node
                Annotations = Node2,
            });            // Sets the Annotation for the Connector
            List<DiagramConnectorAnnotation> Connector1 = new List<DiagramConnectorAnnotation>();
            Connector1.Add(new DiagramConnectorAnnotation()
            {
                Content = "Connector1",
                // Sets the offset for the content
                Offset = 0,
                //Sets the margin for the annotation
                Margin = new DiagramMargin() { Top = 10 },
                Style = new DiagramTextStyle() { Color = "white", Fill = "transparent" }
            });
            List<DiagramConnector> Connectors = new List<DiagramConnector>();
            Connectors.Add(new DiagramConnector()
            {
                Id = "connector1",
                SourceID = "Node1",
                TargetID = "Node2",
                // add the Annotation for the Connector
                Annotations = Connector1
            });

            ViewBag.nodes = Nodes;
            ViewBag.connectors = Connectors;

            List<contextMenuItems> item = new List<contextMenuItems>();
            item.Add(new contextMenuItems()
            {
                Id = "save",
                Text = "Save",
                Target = ".e-elementcontent",
                IconCss = "e-save"
            });
            item.Add(new contextMenuItems()
            {
                Id = "load",
                Text = "Load",
                Target = ".e-elementcontent",
                IconCss = "e-load"
            }); item.Add(new contextMenuItems()
            {
                Id = "clear",
                Text = "Clear",
                Target = ".e-elementcontent",
                IconCss = "e-clear"
            });
            ViewBag.item = item;

            return View();
        }
    }
    public class contextMenuItems
    {
        [DefaultValue(null)]
        [HtmlAttributeName("text")]
        [JsonProperty("text")]
        public string Text
        {
            get;
            set;
        }
        [DefaultValue(null)]
        [HtmlAttributeName("id")]
        [JsonProperty("id")]
        public string Id
        {
            get;
            set;
        }
        [DefaultValue(null)]
        [HtmlAttributeName("target")]
        [JsonProperty("target")]
        public string Target
        {
            get;
            set;
        }
        [DefaultValue(null)]
        [HtmlAttributeName("iconCss")]
        [JsonProperty("iconCss")]
        public string IconCss
        {
            get;
            set;
        }
    }

}

To display the custom context menu items alone, set the showCustomMenuOnly property to true.

Template Support for Context menu

  • Diagram provides template support for context menu. The context menu items can be customized by using the contextMenuBeforeItemRender event. The contextMenuBeforeItemRender event triggers while rendering each menu item.
  • In the following sample, the menu item is rendered with key code for specified action in ContextMenu using the template. Here, the key code is specified for the cut and copy at right corner of the menu items by adding a span element in the contextMenuBeforeItemRender event.
tagHelper
events.cs
<ejs-diagram id="container" width="100%" height="700px" connectors="@ViewBag.connectors" nodes="@ViewBag.nodes">
<e-diagram-contextmenusettings show="true" showCustomMenuOnly="false" ></e-diagram-contextmenusettings>
</ejs-diagram>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Syncfusion.EJ2.Diagrams;
using System.Drawing;

namespace EJ2MVCSampleBrowser.Controllers.Diagram {
    public partial class DiagramController: Controller {
        // GET: Nodes
        public ActionResult Nodes() {

            List < DiagramNode > nodes = new List < DiagramNode > ();
            List < DiagramNodeAnnotation > Node1 = new List < DiagramNodeAnnotation > ();
            Node1.Add(new DiagramNodeAnnotation() {
                Content = "node1", Style = new DiagramTextStyle() {
                    Color = "White", StrokeColor = "None"
                }
            });
            List < DiagramNodeAnnotation > Node2 = new List < DiagramNodeAnnotation > ();
            Node2.Add(new DiagramNodeAnnotation() {
                Content = "node2", Style = new DiagramTextStyle() {
                    Color = "White", StrokeColor = "None"
                }
            });
            nodes.Add(new DiagramNode() {
                Id = "node1",
                    Width = 100,
                    Height = 100,
                    Style = new NodeStyleNodes() {
                        Fill = "darkcyan"
                    },
                    OffsetX = 100,
                    OffsetY = 100,
                    Annotations = Node1
            });
           nodes.Add(new DiagramNode() {
                Id = "node2",
                    Width = 100,
                    Height = 100,
                    Style = new NodeStyleNodes() {
                        Fill = "darkcyan"
                    },
                    OffsetX = 300,
                    OffsetY = 300,
                    Annotations = Node2
            });
            ViewBag.nodes = nodes;

            List<DiagramConnector> Connectors = new List<DiagramConnector>();
            Connectors.Add(new DiagramConnector() { Id = "connector", SourcePoint = new DiagramPoint() { X = 100, Y = 100 }, TargetPoint = new DiagramPoint() { X = 300, Y = 300 }  });
            ViewBag.connectors = Connectors;


            return View();
        }
    }
}

Context menu events

You would be notified with events, when you try to open the context menu items contextMenuOpen and when you click the menu items contextMenuClick. The following code example illustrates how to define those events.

tagHelper
events.cs
<ejs-diagram id="container" width="100%" height="700px" connectors="@ViewBag.connectors" nodes="@ViewBag.nodes">
<e-diagram-contextmenusettings show="true" showCustomMenuOnly="false" ></e-diagram-contextmenusettings>
</ejs-diagram>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Syncfusion.EJ2.Diagrams;
using System.Drawing;

namespace EJ2MVCSampleBrowser.Controllers.Diagram {
    public partial class DiagramController: Controller {
        // GET: Nodes
        public ActionResult Nodes() {

            List < DiagramNode > nodes = new List < DiagramNode > ();
            List < DiagramNodeAnnotation > Node1 = new List < DiagramNodeAnnotation > ();
            Node1.Add(new DiagramNodeAnnotation() {
                Content = "node1", Style = new DiagramTextStyle() {
                    Color = "White", StrokeColor = "None"
                }
            });
            List < DiagramNodeAnnotation > Node2 = new List < DiagramNodeAnnotation > ();
            Node2.Add(new DiagramNodeAnnotation() {
                Content = "node2", Style = new DiagramTextStyle() {
                    Color = "White", StrokeColor = "None"
                }
            });
            nodes.Add(new DiagramNode() {
                Id = "node1",
                    Width = 100,
                    Height = 100,
                    Style = new NodeStyleNodes() {
                        Fill = "darkcyan"
                    },
                    OffsetX = 100,
                    OffsetY = 100,
                    Annotations = Node1
            });
           nodes.Add(new DiagramNode() {
                Id = "node2",
                    Width = 100,
                    Height = 100,
                    Style = new NodeStyleNodes() {
                        Fill = "darkcyan"
                    },
                    OffsetX = 300,
                    OffsetY = 300,
                    Annotations = Node2
            });
            ViewBag.nodes = nodes;

            List<DiagramConnector> Connectors = new List<DiagramConnector>();
            Connectors.Add(new DiagramConnector() { Id = "connector", SourcePoint = new DiagramPoint() { X = 100, Y = 100 }, TargetPoint = new DiagramPoint() { X = 300, Y = 300 }  });
            ViewBag.connectors = Connectors;


            return View();
        }
    }
}
function contextMenuOpen() {
    for (var item of args.items) {
                if (item.text === 'delete') {
                    var diagram = document.getElementById("container").ej2_instances[0];
                    if (!diagram.selectedItems.nodes.length && !diagram.selectedItems.connectors.length) {
                        args.hiddenItems.push(item.text);
                    }
                }
            }
    }

function contextMenuClick() {
    if (args.item.id === 'delete') {
                var diagram = document.getElementById("container").ej2_instances[0];
                if ((diagram.selectedItems.nodes.length + diagram.selectedItems.connectors.length) > 0) {
                    diagram.cut();
                }
            }

}
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