gistfile1.cs

public static HelperResult EditField<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression)
{
  var path = "/Templates/Partials/EditField/" + (template ?? "Default") + ".cshtml";
  var page = WebPageBase.CreateInstanceFromVirtualPath(path);
  var context = new WebPageContext(new HttpContextWrapper(HttpContext.Current), page, null);

  var modelMetaData = ModelMetadata.FromLambdaExpression(expression, html.ViewData);

  var fieldname = ExpressionHelper.GetExpressionText(expression);
  context.PageData["Validation"] = html.GetUnobtrusiveValidationAttributes(fieldname, modelMetaData);
}