Tutorial 1: Loading graph data

This tutorial shows how to load graph data from XML and create diagram objects corresponding to the graph nodes and edges. It assumes you have followed the Getting Started guide to add <DiagramView> component, and the project name is Tutorial1. A copy of the completed tutorial project is available under Samples folder of BlazorDiagram distribution.

1. Right-click the project in Solution Explorer and choose Add -> New Item from the context menu. Create a new XML file called SampleGraph.xml and add to it content in the following form:

XML

<?xml version="1.0" encoding="utf-8" ?>
<Graph>
    <Nodes>
        <Node id="0" name="start" />
        <Node id="1" name="activity 1" />
        <Node id="2" name="task 1" />
        <Node id="3" name="task 2" />
        <Node id="4" name="activity 2" />
        <Node id="5" name="task 3" />
        <Node id="6" name="task 4" />
        <Node id="7" name="activity 3" />
        <Node id="8" name="task 5" />
        <Node id="9" name="task 6" />
        <Node id="10" name="end" />
    </Nodes>
    <Links>
        <Link origin="0" target="1" />
        <Link origin="1" target="2" />
        <Link origin="1" target="3" />
        <Link origin="2" target="4" />
        <Link origin="3" target="4" />
        <Link origin="4" target="5" />
        <Link origin="4" target="6" />
        <Link origin="5" target="10" />
        <Link origin="6" target="10" />
        <Link origin="0" target="7" />
        <Link origin="7" target="8" />
        <Link origin="8" target="9" />
        <Link origin="1" target="9" />
        <Link origin="9" target="10" />
    </Links>
</Graph>

2. Set the file's "Build Action" property to "Embedded resource".

3. Add an OnAfterRender override to the page's @code section:

C#

protected override void OnAfterRender(bool firstRender)
{
    base.OnAfterRender(firstRender);

    if (firstRender)
    {
    }
}

4. Add the following variables to OnAfterRender inside the firstRender block. "nodeMap" maps diagram nodes to their identifiers, and "bounds" contains the default node size.

C#

var nodeMap = new Dictionary<string, DiagramNode>();
var bounds = new Rect(0, 0, 20, 8);

5. Load the XML document using the XML DOM API:

C#

// Load the graph xml
var assembly = typeof(App).GetTypeInfo().Assembly;
var stream = assembly.GetManifestResourceStream("Tutorial1.SampleGraph.xml");

string text;
using (var reader = new StreamReader(stream))
    text = reader.ReadToEnd();
var document = XDocument.Parse(text);

6. Load the graph node elements and create their corresponding ShapeNode objects by calling the CreateShapeNode method of the Factory class. CreateShapeNode is just a shortcut to creating a ShapeNode instance using the "new" operator and adding it to the Nodes collection of the diagram. Additionally, this code maps the new node to the "id" attribute of the XML element, and sets the node's Text to the value of the "name" attribute.

C#

// load node data
var nodes = document.Descendants("Node");
foreach (var node in nodes)
{
    var diagramNode = diagram.Factory.CreateShapeNode(bounds);
    nodeMap[node.Attribute("id").Value] = diagramNode;
    diagramNode.Text = node.Attribute("name").Value;
}

7. Load the graph links and create corresponding DiagramLink objects. The Origin and Destination of the links are accessed by their ids through the "nodeMap" dictionary.

C#

// load link data
var links = document.Descendants("Link");
foreach (var link in links)
{
    diagram.Factory.CreateDiagramLink(
        nodeMap[link.Attribute("origin").Value],
        nodeMap[link.Attribute("target").Value]).
    HeadShapeSize = 2;
}

8. Arrange the diagram using the LayeredLayout class.

C#

// arrange the graph
var layout = new LayeredLayout();
layout.LayerDistance = 12;
layout.NodeDistance = 25;
layout.Arrange(diagram);

9. Build and run the project. If everything is fine, you should see this representation of the graph: