cannot rename Model in dropdownlistfor

Question

I want to add Dropdownlist in my MVC application but I have an error. 

 

 CS0135: 'Model' conflicts with the declaration 'System.Web.Mvc.WebViewPage<TModel>.Model'

 

This is my razor code for dropdownlist

 

@Html.DropDownListFor(a => a.UserId, new SelectList(Model.UserItems, "Id", "UserName"));

 

*Most of the reference said I cannot use Model in select list. But I cannot rename to others. Kindly support if you have any ways.