An extension method for ProjectTargetElement that ensures the project has the correct UsingTask

ProjectTargetElementExtensions.cs

using System.Linq;
using Microsoft.Build.Construction;

static class ProjectTargetElementExtensions
{
    public static ProjectTaskElement AddTask<TTask>(this ProjectTargetElement projectTargetElement)
    {
        string taskName = typeof (TTask).Name;
        ProjectRootElement projectRootElement = projectTargetElement.ContainingProject;

        if (!projectRootElement.UsingTasks.Any(ut => ut.TaskName == taskName))
        {
            projectRootElement.AddUsingTask<TTask>();
        }

        return projectTargetElement.AddTask(taskName);
    }
}

Requires https://gist.github.com/JayBazuzi/7519677