i am going to minimize no. of code lines and directly bind instead of add columns when i do this show error

public DataTable vehcile(string id)
{
   Entities1 wr = new Entities1();
   GridView1.DataSource=wr.spvechile(id);
   GridView1.DataBind();
   return ;
}
 protected void Page_Load(object sender, EventArgs e)
 {
     if(!this.IsPostBack)
     {
        this.vehcile(id);
     }
}

this show error

Error 10 An object of a type convertible to 'System.Data.DataTable' is required Error 9 The name 'id' does not exist in the current context now how i return data and how i set data source?

any solution's?