Question

I found an nice code example for type validation:

public class StringViewModel : ViewModelBase, IComparable
{
    private string _value;
    private string _originalValue;

    public StringViewModel(string value)
    {
        _value = value;
        _originalValue = value;
    }

    // Der eigentliche Wert.
    public string Value
    {
        get { return _value; }
        set
        {
            if (value != _value)
            {
                _value = value;
                RaisePropertyChanged("Value");
                HasChanges = _value != _originalValue && !(string.IsNullOrEmpty(_value) && string.IsNullOrEmpty(_originalValue));
            }
        }
    }

    public override void AcceptChanges()
    {
        _originalValue = _value;
        HasChanges = false;
        HasError = false;
    }

    public override void UndoChanges()
    {
        Value = _originalValue;
        HasError = false;
    }

    // Muss implementiert werden, damit die Sortierung im CollectionView funktioniert.
    public int CompareTo(object obj)
    {
        if (obj == null) return 1;
        if (object.ReferenceEquals(this, obj)) return 0;
        StringViewModel other = obj as StringViewModel;
        return string.Compare(this._value, other._value);
    }

    public override string ToString()
    {
        return _value;
    }
}

Now I want do make it more generic, so I need to create the 2 values below at runtime:

private T? _value;
private T? _originalValue;

because I want to do something like:

public class ItemModel : IComparable, INotifyEXTEND
{
    private ??? _value;
    private ??? _originalValue;

    public ItemModel(string value)
    {
            _value = value;
            _originalValue = value;
    }

    public ??? Value
    {
        get { return _value; }
        set
        {
            if (value != _value)
            {
                _value = value;
                RaisePropertyChanged("Value");
                HasChanges = _value != _originalValue && !(string.IsNullOrEmpty(_value) && string.IsNullOrEmpty(_originalValue));
            }
        }
    }

    public override void AcceptChanges()
    {
        _originalValue = _value;
        HasChanges = false;
        HasError = false;
    }

    public override void UndoChanges()
    {
        Value = _originalValue;
        HasError = false;
    }

    public int CompareTo(object obj)
    {
        if (obj == null) return 1;
        if (object.ReferenceEquals(this, obj)) return 0;
        ??? other = obj as ???;
        return string.Compare(this._value, other._value);
    }

    public override string ToString()
    {
        return _value;
    }
}

So I can use it like this:

public class PersonViewModel : ViewModelBase
{

    private Person _person;
    private ItemModel _lastname;
    private ItemModel _birthdate;
    private bool _isNew;

    // Otherstuff
}

Any suggestions on how to do this? (Some example code snippets or links would be nice)

Answer 1

You need to use generics:

public class ItemModel<T> : IComparable<ItemModel<T>>, INotifyEXTEND where T : IComparable<T>