T4 Template that creates an ObservableListSource in the <project-name>.DataBinding Namespace. This is what Navigation Properties should use for EF6+WinForms compatibility.

Database.DataBinding.tt

<#@ template language="C#" debug="false" hostspecific="true" #>
<#@ output extension=".cs" #>
<#@ assembly name="System" #>
<#@ import namespace="System.Collections" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ assembly name="System.Core" #>
<#@ assembly name="System.Data.Entity" #>
<#@ import namespace="System.IO" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Reflection" #>
<#@ assembly name="EnvDTE" #>
<#@ import namespace="EnvDTE" #>
<#@ assembly name="System.Data.Entity.Design" #>
<#@ import namespace="System.Data.Entity.Design.PluralizationServices" #>

<#
    // TODO: Place calls here to class-feature method calls.
    
    InitializeActiveProjectAndSolution();
#>
<#=        GenerateFileHeader()#>

using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Data.Entity;

// ReSharper disable once CheckNamespace
namespace <#=this.DataBindingLayerNameSpace#>
{
<#    PushIndent("    "); #>
/// <summary>
///     This is a collection that is compatible with Windows Forms' data-bound
///     controls, as it allows Windows Forms graphical, data-bound presentation
///     controls to engage in two-way communications with memory objects. Please
///     also derive all your entities' navigation properties from this class by
///     modifying the Entities.Context.tt and Entities.tt T4 templates in your
///     Data Access Layer.
/// </summary>
/// <typeparam name="T">Name of the entity object being wrapped by this collection.</typeparam>
public class ObservableListSource<T> : ObservableCollection<T>, IListSource
where T : class
{
<#    PushIndent("    "); #>
/// <summary>
///     Constructs a new instance of
///     <see cref="T:<#=this.DataBindingLayerNameSpace#>.ObservableListSource" /> and returns a
///     reference to it.
/// </summary>
public ObservableListSource() { }

/// <summary>
///     Constructs a new instance of
///     <see cref="T:<#=this.DataBindingLayerNameSpace#>.ObservableListSource" /> and returns a
///     reference to it.
/// </summary>
/// <param name="collection">
///     Enumerable collection of objects of
///     <typeparamref name="T" />.
/// </param>
public ObservableListSource(IEnumerable<T> collection) : base(collection) { }

/// <summary>
///     Gets a value indicating whether the collection is a collection of
///     <see cref="T:System.Collections.IList" /> objects.
/// </summary>
/// <returns>
///     <see langword="true" /> if the collection is a collection of
///     <see cref="T:System.Collections.IList" /> objects; otherwise,
///     <see langword="false" />.
/// </returns>
bool IListSource.ContainsListCollection
{
    get { return false; }
}

/// <summary>
///     Gets a reference to an instance of this collection that implements the
///     <see cref="T:System.ComponentModel.IBindingList" /> interface.
/// </summary>
public IBindingList List { get; private set; }

/// <summary>
///     Returns an <see cref="T:System.Collections.IList" /> that can be bound
///     to a data source from an object that does not implement an
///     <see cref="T:System.Collections.IList" /> itself.
/// </summary>
/// <returns>
///     An <see cref="T:System.Collections.IList" /> that can be bound to a
///     data source from the object.
/// </returns>
IList IListSource.GetList()
{
    return List ?? (List = this.ToBindingList());
}
<#    PopIndent(); #>
}
<#    PopIndent(); #>
}
<#    CreateFile("ObservableListSource.cs"); #>
<#+
    /// <summary>
    /// Generates a header comment for the file so that users of the file know that it's generated from a template.
    /// </summary>
    public string GenerateFileHeader() 
    {
        return "//------------------------------------------------------------------------------\r\n// <auto-generated>\r\n//     This code was generated from a template.\r\n//\r\n//     Manual changes to this file may cause unexpected behavior in your application.\r\n//     Manual changes to this file will be overwritten if the code is regenerated.\r\n// </auto-generated>\r\n//------------------------------------------------------------------------------";
    }
   
    /// <summary>
    /// Gets or sets a reference to the currently-active project in the integrated development environment (IDE).
    /// </summary>
    private Project ActiveProject { get; set; }

    /// <summary>
    /// Gets or sets a reference to the currently-active solution in the integrated development environment (IDE).
    /// </summary>
    private Solution ActiveSolution { get; set; }

    /// <summary>
    /// Gets or sets a reference to the top-level object in the Visual Studio automation object model.
    /// </summary>
    private DTE DTE { get; set; }

    /// <summary>
    /// Gets a string that contains the C# namespace name for the business layer.
    /// </summary>
    /// <remarks>
    /// The business layer is the tier of your solution that contains classes generated from this T4 template.
    /// </remarks>
    private string BusinessLayerNameSpace {
        get {
            return ActiveProject == null ? string.Empty : string.Format(
                "{0}.BusinessLayer", ActiveProject.Name
                );
        }  
    }

    /// <summary>
    /// Gets a string that contains the C# namespace name for the data-binding layer.
    /// </summary>
    /// <remarks>
    /// The data-binding layer is where we implement useful classes that are utilized by
    /// Windwos Forms for data-binding.
    /// </remarks>
    private string DataBindingLayerNameSpace {
        get {
            return ActiveProject == null ? string.Empty : string.Format(
                "{0}.DataBinding", ActiveProject.Name
                );
        }  
    }

    /// <summary>
    /// Interrogates the Visual Studio object model to locate references to
    /// the currently-active Solution and Project.
    /// </summary>
    public void InitializeActiveProjectAndSolution()
    {
        IServiceProvider serviceProvider = (IServiceProvider)this.Host;
        this.DTE = serviceProvider.GetService(typeof(DTE)) as DTE; 
        ActiveSolution = this.DTE.Solution;
        ActiveProject = GetActiveProject();     
    }

    //Generating Seperate Files
    public void ProcessContent(string outputFileName, string content)
    {
        if (string.IsNullOrWhiteSpace(outputFileName)) throw new ArgumentNullException(nameof(outputFileName));
        if (string.IsNullOrWhiteSpace(content)) throw new ArgumentNullException(nameof(content));

        var templateDirectory = Path.GetDirectoryName(Host.TemplateFile);
        var outputFilePath = Path.Combine(templateDirectory, outputFileName);
        var outputDirectoryPath = Path.GetDirectoryName(outputFilePath);        

        if(!Directory.Exists(outputDirectoryPath))
            Directory.CreateDirectory(outputDirectoryPath);

        if (File.Exists(outputFilePath))    // always overwrite existing output
            File.Delete(outputFilePath);

        File.WriteAllText(outputFilePath, content);

        IServiceProvider hostServiceProvider = (IServiceProvider)Host;
        EnvDTE.DTE dte = (EnvDTE.DTE)hostServiceProvider.GetService(typeof(EnvDTE.DTE));
        ProjectItem containingProjectItem = dte.Solution.FindProjectItem(Host.TemplateFile);
        containingProjectItem.ProjectItems.AddFromFile(outputFilePath);
        
    }

    public string GetDataSourceName(string efContext)
    {
        if (string.IsNullOrWhiteSpace(efContext)) throw new ArgumentNullException(nameof(efContext));

        return efContext
            .Replace("Entities", "")
            .Replace("DbContext", "")
            .Replace("Db", "")
            .Replace("Context", "");
    }

    public void CreateFile(string fileName)
    {
        if (string.IsNullOrWhiteSpace(fileName)) throw new ArgumentNullException(nameof(fileName));

        ProcessContent(fileName, this.GenerationEnvironment.ToString().TrimStart());
        this.GenerationEnvironment.Remove(0, this.GenerationEnvironment.Length);
    }

    //Get Projects
    public Project GetActiveProject()
    {
        Project activeProject = null;
 
        Array activeSolutionProjects = this.DTE.ActiveSolutionProjects as Array;
        if (activeSolutionProjects != null && activeSolutionProjects.Length > 0)
            activeProject = activeSolutionProjects.GetValue(0) as Project;
        return activeProject;
    }

    public List<CodeClass> FindClasses(Project project, string ns, string className) 
    {
        List<CodeClass> result = new List<CodeClass>();
        FindClasses(project.CodeModel.CodeElements, className, ns, result, false);
        return result;
    }

    private void FindClasses(CodeElements elements, string className, string searchNamespace, List<CodeClass> result, bool isNamespaceOk) 
    {
        if (elements == null) return;
        foreach (CodeElement element in elements) 
        {
            if (element is CodeNamespace) 
            {
                CodeNamespace ns = element as CodeNamespace;
                if (ns != null) 
                {
                    if (ns.FullName == searchNamespace)
                        FindClasses(ns.Members, className, searchNamespace, result, true);
                    else
                        FindClasses(ns.Members, className, searchNamespace, result, false);
                }
            } 
            else if (element is CodeClass && isNamespaceOk) 
            {
                CodeClass c = element as CodeClass;
                if (c != null) 
                {
                    if (c.FullName.Contains(className))
                        result.Add(c);

                    FindClasses(c.Members, className, searchNamespace, result, true);
                }
            }
        }
    }
        
    //Naming
    public string GetProperClassName(string className)
    {
        string returnString = className;
        returnString = returnString.Replace(" ", "_");
        returnString = returnString.Replace("_", " ");
        //TextInfo ti = CultureInfo.CurrentCulture.TextInfo;  
        //returnString = ti.ToTitleCase(returnString);
        returnString = returnString.Replace(" ", "");
        return returnString;
    }

    private static string CharToUpper(string input, int position)
    {
        return input.First().ToString().ToUpper() + input.Substring(position+1);
    }
#>