How to pass a JSON Object to a method in webservice?

I'm trying to pass a JSON Object to a method in my controller and I'm not getting it, the problem is that the email field always returns null.

How to do this?

I'm trying like this.

JSON Object

{"UsuarioJsonModel": {"email":"[email protected]", "senha":"xxxxxx"}}

Model

public class UsuarioJsonModel 
{

    public long id                  { get; set; }         
    public String nome              {   get;set;}            
    public String email             {get;set;}    
    public String senha             {get;set;}   
    public int status               { get; set; } //1 ativo, 2 inativo, 0 aguardando
    public int tipo                 { get; set; } //1 painel, 2 aplicativos
    public String imagem            { get; set; }
    public int loginBy              { get; set; } //0 app, 1 facebook
    public UsuarioJsonModel() { }

}

Method that receives JSON Object

[WebMethod]
[HttpPost]
public JsonResult doLoginApp(UsuarioJsonModel model)
{ 
    jsonResposta.Add("status", "1");
    jsonResposta.Add("email", model.email);
    return Json(jsonResposta);
}