Testing to create a GadgetMetric in my solution using the guidelines but get compile errors (EPiServer CMS 6 R2, with latest GA plugin)

'System.ComponentModel.Composition.ExportAttribute' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.ComponentModel.Composition, Version=2009.22.10.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7'.

But System.CompinentModel.Composition is already referenced, my web.config:

<dependentAssembly>
<assemblyIdentityname="System.ComponentModel.Composition"publicKeyToken="8fe83dea738b45b7"culture="neutral"/>
<bindingRedirectoldVersion="1.0.0.0-2009.22.10.0"newVersion="2009.22.10.0"/>
</dependentAssembly>

Error 2 'EPiServer.GoogleAnalytics.Analytics.GadgetMetricAttribute' is not an attribute class 

This is my simple code, added the class to root:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using EPiServer.GoogleAnalytics;
using EPiServer.GoogleAnalytics.Analytics;
using EPiServer.GoogleAnalytics.Analytics.Models;


namespace EPiServer.GoogleAnalytics.Analytics
{
    [GadgetMetric]
    public class TestGa : ListMetricBase
    {
        public override string Metric
        {
            get { return "ga:pageviews"; }
        }

        public override string Dimension
        {
            get
            {
                return "ga:pageTitle";
            }
        }
    }
}

What is missing?