GraphML is a comprehensive and easy-to-use file format for graphs. QuickGraph supports loading and saving directed graphs to this format. The GraphML serialization APIs are exposed through the GraphMLExtensions extension methods (in QuickGraph.Serialization).

The serialization code uses dynamic code generation to provide high performance in reading and writing custom properties.

To serialize a graph, simply call the SerializeToGraphML extension methods with an XmlWriter instance.

var g = new AdjacencyGraph<int, Edge<int>>();
...
using(var xwriter = XmlWriter.Create(...))
    g.SerializeToGraphML(xwriter);

To deserialize a graph, create the graph instance and call the DeserializeFromGraphML:

var g = new AdjacencyGraph<int, Edge<int>>();
using(var xreader = XmlReader.Create(...))
     g.DeserializeFromGraphML(xreader,
         id => int.Parse(id),
         (source, target, id) => new Edge<int>(source, target)
     );

The serializer supports the XmlAttribute attribute on public properties of the vertex, edge and graph types. These properties will be declared and serialized in the GraphML stream. The supported property types are bool, int, long, float, double and string.

class IntEdge : Edge<int> {
   ...
   [XmlAttribute("name")](XmlAttribute(_name_))
   public string Name {get;set;}
}

Default values can also be specified for the properties by using the DefaultValue attribute:

   ...
   [XmlAttribute("name")](XmlAttribute(_name_))
   [DefaultValue("unknown")](DefaultValue(_unknown_))
   public string Name {get;set;}