Simplifying Contact Facets with C# 6

Contact Facets allow you to persist information about visitors into the Sitecore xDB. We’re not going to get into the theory behind them in this post; for that go read Pete Navarra’s great blog post that summarizes current practices and how to add facets.

Today we’re going to discuss how to syntactically improve the declaration of a contact facet class using syntaxes available in C# 6.0 (VS 2015) and C# 7.0 (VS 2017). It’s important to note that the C# version is decoupled from the .NET framework version: the C# 7.0 compiler is perfectly capable of emitting C# 7 syntax to a .NET 4.5-targeted assembly, for instance. So you can use these modern language features as long as you’ve got the right version of MSBuild or Visual Studio :)

Here’s the example Pete uses in his post, which follows other examples out there as well:

using System;
using Sitecore.Analytics.Model.Framework;
 
namespace SitecoreHacker.Sandbox.Facets
{
    [Serializable]
    public class MarketingData: Facet, IMarketingData
    {
 
        private const string CUSTOMER_ID = "CustomerId";
        private const string SEGEMENT = "Segment"; // sic :p
 
        #region Properties
        public string CustomerId
        {
            get { return GetAttribute<string>(CUSTOMER_ID); }
            set { SetAttribute(CUSTOMER_ID, value); }
        }
 
        public string Segment
        {
            get { return GetAttribute<string>(SEGEMENT); }
            set { SetAttribute(SEGEMENT, value); }
        }
        #endregion
         
        public MarketingData()
        {
            EnsureAttribute<string>(CUSTOMER_ID);
            EnsureAttribute<string>(SEGEMENT);
        }
    }
}

As you can see, the facet API requires string keys for the facet values - in this case stored as const string - to get and set them. Further, as Pete notes:

I found out the hard way that the constants defined, the value must equal the actual name of the class property for the same attribute.

Well in C# 6 (VS 2015), there’s a syntax for that. The nameof statement allows you to get the string name of a variable or property. This essentially hands off the management and maintenance of the const value to the compiler, instead of the developer.

So we can clean up this example by using nameof instead of constants - and get as a bonus refactoring support and compile-time validation of the names:

using System;
using Sitecore.Analytics.Model.Framework;
 
namespace Elephant.Sandbox.Facets
{
    [Serializable]
    public class MarketingData: Facet, IMarketingData
    {
        public string CustomerId
        {
            get { return GetAttribute<string>(nameof(CustomerId)); }
            set { SetAttribute(nameof(CustomerId), value); }
        }
 
        public string Segment
        {
            get { return GetAttribute<string>(nameof(Segment)); }
            set { SetAttribute(nameof(Segment), value); }
        }
         
        public MarketingData()
        {
            EnsureAttribute<string>(nameof(CustomerId));
            EnsureAttribute<string>(nameof(Segment));
        }
    }
}

Finally if you have C# 7.0 (VS 2017), you can also utilize expression bodied members to further clean up the property syntax:

using System;
using Sitecore.Analytics.Model.Framework;
 
namespace Rhino.Sandbox.Facets
{
    [Serializable]
    public class MarketingData: Facet, IMarketingData
    {
        public string CustomerId
        {
            // expression bodied members turn the single-expression get 
            // into a lamdba-style syntax, removing the need for braces
            get => GetAttribute<string>(nameof(CustomerId));
            set => SetAttribute(nameof(CustomerId), value);
        }
 
        public string Segment
        {
            get => GetAttribute<string>(nameof(Segment));
            set => SetAttribute(nameof(Segment), value);
        }
         
        public MarketingData()
        {
            EnsureAttribute<string>(nameof(CustomerId));
            EnsureAttribute<string>(nameof(Segment));
        }
    }
}

So there - now go forth and put your data in the xDB :)