Create a custom model

Create a new project - for example, Documentation.Model.

Define facets and events.

using Sitecore.XConnect;
using System;

namespace Documentation.Model
{
    [Serializable]
    [FacetKey(DefaultFacetKey)]
    public class FrequentFlyerInfo : Sitecore.XConnect.Facet
    {
        public const string DefaultFacetKey = "FrequentFlyerInfo";

        public FrequentFlyerInfo(string frequentFlyerId)
        {
            FrequentFlyerID = frequentFlyerId;
        }

        public FrequentFlyerStatus Status { get; set; }
        public string FrequentFlyerID { get; set; } // Example: ABC12345

        public enum FrequentFlyerStatus
        {
            Unknown = 0,
            Bronze,
            Silver,
            Gold
        }
    }

    public class BoardFlight : Event
    {
        public static readonly Guid EventDefinitionId = new Guid("2A72E131-BCFD-481C-8E15-04496E9586DC");

        public BoardFlight(DateTime timestamp) : base(EventDefinitionId, timestamp)
        {

        }

        public string Seat { get; set; }
        public bool Upgraded { get; set; }
    }
}

Create a class named CollectionModel - for example, Documentation.Model.CollectionModel. Create an instance of the XdbModelBuilder as shown:

using Sitecore.XConnect;
using Sitecore.XConnect.Schema;
using System;

namespace Documentation.Model
{
    public class CollectionModel
    {
        public static XdbModel Model { get; } = BuildModel();

        private static XdbModel BuildModel()
        {
            XdbModelBuilder modelBuilder = new XdbModelBuilder("DocumentationModel", new XdbModelVersion(1, 0));

            // Facets and events here

            return modelBuilder.BuildModel();
        }
    }
}

Optionally, reference another model that you want to use. In the following example, the Sitecore.XConnect.Collection.Model.CollectionModel.Model is referenced. Classes such as Facet and Event are included automatically.

using Sitecore.XConnect;
using Sitecore.XConnect.Schema;
using System;

namespace Documentation.Model
{
    public class CollectionModel
    {
        public static XdbModel Model { get; } = BuildModel();

        private static XdbModel BuildModel()
        {
            XdbModelBuilder modelBuilder = new XdbModelBuilder("DocumentationModel", new XdbModelVersion(1, 0));

            modelBuilder.ReferenceModel(Sitecore.XConnect.Collection.Model.CollectionModel.Model);
            // Facets and events here

            return modelBuilder.BuildModel();
        }
    }
}

Define the FrequentFlyerInfo contact facet and the BoardFlight event:

using Sitecore.XConnect;
using Sitecore.XConnect.Schema;
using System;

namespace Documentation
{
    public class CollectionModel
    {
        public static XdbModel Model { get; } = BuildModel();

        private static XdbModel BuildModel()
        {
            XdbModelBuilder modelBuilder = new XdbModelBuilder("DocumentationModel", new XdbModelVersion(1, 0));

            modelBuilder.ReferenceModel(Sitecore.XConnect.Collection.Model.CollectionModel.Model);

            modelBuilder.DefineFacet<Contact, FrequentFlyerInfo>(FrequentFlyerInfo.DefaultFacetKey);
            modelBuilder.DefineEventType<BoardFlight>(false);

            return modelBuilder.BuildModel();
        }
    }
}

If facets, events, or types inherit a type that is located in a different assembly, use the modelbuilder.RegisterType() method to manually register a type. For example, Documentation.Model.FrequentFlyerInfo might inherit Common.Model.InheritedBase.

using Sitecore.XConnect;
using Sitecore.XConnect.Schema;
using System;

namespace Documentation
{
    public class CollectionModel
    {
        public static XdbModel Model { get; } = BuildModel();

        private static XdbModel BuildModel()
        {
            XdbModelBuilder modelBuilder = new XdbModelBuilder("DocumentationModel", new XdbModelVersion(1, 0));

            modelBuilder.ReferenceModel(Sitecore.XConnect.Collection.Model.CollectionModel.Model);

            modelBuilder.RegisterType<Common.Model.InheritedBase>(false);

            modelBuilder.DefineFacet<Contact, FrequentFlyerInfo>(FrequentFlyerInfo.DefaultFacetKey);
            modelBuilder.DefineEventType<BoardFlight>(false);

            return modelBuilder.BuildModel();
        }
    }
}