MVC - Fix Error - The type or namespace name 'RemoteAttribute' could not be found

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The type or namespace name 'RemoteAttribute' could not be found (are you missing a using directive or an assembly reference?)   

The type or namespace name 'Remote' could not be found (are you missing a using directive or an assembly reference?)  

The type or namespace name 'ErrorMessage' could not be found (are you missing a using directive or an assembly reference?)  

when 

        [Remote(action: "DoSomething", controller: "Home", ErrorMessage ="some error")]
        public string Name { get; set; }

To fix it add

    using System.Web.Mvc;