call stored procedure with parametes using web api : When I execute this Stored Procedure in MS SQL Server:

 **use Vcom**

  **go**

  **exec abrir_turno @posto = 'pppe', @turno = '3', @data = '2016-06-13'** 

The SQL return a messagem " **your SP set pppe to open** ".

I am trying to implement that using Web Api 2with c#:  

**public IEnumerable<string> spabrirturno(string posto, string turno, string data, string STATUS_TURNO)**
{
   
   STATUS_TURNO = null;
            
   return obj.abrir_turno(posto, turno, data, STATUS_TURNO).AsEnumerable();

}

But that is a error : "cannot implicitly convert type ienumerable to string" message in photo... 

[enter image description here][1]


  [1]: http://i.stack.imgur.com/Uhbvb.png