Why Object can't be find it?

Hi,

I have 2 classes.

The line           
return Foods.First(x => x._id == id);

Gives me an error
Error 1 'Check_Eat.Food' does not contain a definition for '_id' and no extension method '_id' accepting a first argument of type 'Check_Eat.Food' could be found (are you missing a using directive or an assembly reference?) 

What I am doing wrong?
Thanks

namespace Check_Eat.Models
{
    public class Food : INotifyPropertyChanged
    {
     
        #region Properties
        private int id;
        public int _id
        {
            get
            {
                return id;
            }
            set
            {
                if (id != value)
                {
                    id = value;
                    OnNotifyPropertyChanged("_id");
                }
            }
        }
       
        private string _code = string.Empty;
        public string code
        {
            get
            { return _code; }

            set
            {

                if (_code != value)
                {
                    _code = value;
                    OnNotifyPropertyChanged("code");
                }
            }
        }

        private string _category = string.Empty;
        public string category
        {
            get
            { return _category; }

            set
            {
                if (_category != value)
                {
                    _category = value;
                    OnNotifyPropertyChanged("category");
                }
            }
        }

        private string _description = string.Empty;
        public string description
        {
            get
            { return _description; }

            set
            {
                if (_description != value)
                {
                    _description = value;
                    OnNotifyPropertyChanged("description");
                }
            }
        }

        private string _calories = string.Empty;
        public string calories
        {
            get
            { return _calories; }

            set
            {
                if (_calories != value)
                {
                    _calories = value;
                    OnNotifyPropertyChanged("calories");
                }
            }
        }

        private string _serving = string.Empty;
        public string serving
        {
            get
            { return _serving; }

            set
            {
                if (_serving != value)
                {
                    _serving = value;
                    OnNotifyPropertyChanged("serving");
                }
           
            }
        }

        #endregion "Properties"

        #region INotifyPropertyChanged Interface
        public event PropertyChangedEventHandler PropertyChanged;

        private void OnNotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion
    }
}

namespace Check_Eat.ViewModels
{
    public class FoodViewModel : INotifyPropertyChanged
    {
        #region Fields and Properties

        // This property will be bound to GridView's ItemsDataSource property for providing data
        private ObservableCollection<Food> foods;

        // This property will be bound to button's Command property for deleting item
        public IDelegateCommand DeleteCommand { protected set; get; }

        public ObservableCollection<Food> Foods
        {
            get
            {
                return foods;
            }
            set
            {
                if (foods != value)
                {
                    foods = value;
                    OnPropertyChanged("Foods");
                }
            }
        }

        #endregion

        #region Constructor
        public FoodViewModel()
        {
            // create a DeleteCommand instance
            this.DeleteCommand = new DelegateCommand(ExecuteDeleteCommand);

            // Get data source
            Foods = InitializeSampleData.GetData();
        }
        #endregion

        #region Execute and CanExecute methods
       void ExecuteDeleteCommand(object param)
        {
            int id = (Int32)param;
            Food cus = GetFoodById(id);
            if (cus != null)
            {
                Foods.Remove(cus);
            }
        }

        #endregion
        // Get the deleting item by Id property
        private Food GetFoodById(int id)
        {
            return Foods.First(x => x._id == id);
        }
        #region INotifyPropertyChanged
        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion
    }
}

ADRIAN DIBU