是否可以“扩展”财产“类”？

Question

I'm new to C# (started last week) so be cool with me ;). I'd like to know if I can somehow write a custom property, let me explain:

I have some partial classes that I complete by adding properties, but the pattern of all the getters and setters are the same so I'd like to factorize this:

public partial class Travel
{
    public String TravelName
    {
        get
        {
            return LocaleHelper.GetRessource(Ressource1);
        }
        set
        {
            if (this.Ressource1 == null)
                Ressource1 = new Ressource() { DefaultValue = value };
            else
                Ressource1.DefaultValue = value;
        }
    }

    public String TravelDescription
    {
        get
        {
            return LocaleHelper.GetRessource(Ressource2);
        }
        set
        {
            if (this.Ressource2 == null)
                Ressource2 = new Ressource() { DefaultValue = value };
            else
                Ressource2.DefaultValue = value;
        }
    }
}

As you can see, the only thing that change is Ressource1/Ressource2. My goal is be able to write something like:

public partial class Travel
{
    public LocalizedString TravelName(Ressource1);

    public LocalizedString TravelDescription(Ressource2);
}

Anybody have an idea to make this, or another idea to make my code cleaner? Thank you,

Guillaume

Answer 1

There is no facility to do this inside C# or .NET itself, but if you are doing lots of these it may be worth investigating aspect orientated programming through postsharp . Basically it will allow you to define an attribute that causes extra code to be injected at compile time. The code you type be something like:

public partial class Travel
{
    [LocalizedProperty(source = "Ressource1")
    public string TravelName { get; set; }

    [LocalizedProperty(source = "Ressource2")
    public string TravelDescription{ get; set; }
}

And at compile time PostSharp will replace the property with a template you have defined in the new LocalizedPropertyAttribute class.

Answer 2

You can't make it quite as succinct as what you describe, but you can decrease the complexity and redundancy of the setters.

private void SetRessource(ref Ressource res, string value)
{
    if(res == null) res = new Ressource();

    res.DefaultValue = value;
}

public String TravelName
{
    get { return LocaleHelper.GetRessource(Ressource1); }
    set { SetRessource(ref this.Ressource1, value); }
}

public String TravelDescription
{
    get { return LocaleHelper.GetRessource(Ressource2); }
    set { SetRessource(ref this.Ressource2, value); }
}

Answer 3

I don't know exactly what you are trying to achieve, but you may be making things too complicated. Wouldn't this be sufficient?

public class Travel
{
   /// <summary>
   /// Creates a new instance of <see cref="Travel"/>.
   /// </summary>
   public Travel()
   {
      this.TravelName = Resources.DefaultTravelName;
      this.TravelDescription = Resources.DefaultTravelDescription;
   }

   public string TravelName { get; set; }

   public string TravelDescription { get; set; }
}

where Resources is a generated class (from a resx file) for localized resources. I have a feeling you are trying to build your own localization framework because you don't know yet that .NET already has infrastructure for that .

Answer 4

No, there is no such way. It would be possible in php but not in C#.

You should change your approach away from properties in this case.

UPD: Probably you could use something like this for every property (except for it's obvious weakness):

public class Prop
{
    Resource _res;

    public Prop(Resource res)
    {
        this._res = res;
    }

    public string Value
    {
        get
        {
            return LocaleHelper.GetRessource(_res);
        }
        set
        {
            if(_res == null)
                // This is a weak point as it's now
                // as it wont work
            else
                _res.DefaultValue = value;
        }
}

Answer 5

You could implement a single indexed property, giving you one of the following two syntax choices based on your preference. The code would basically be a function that accepts the specifically named resource and returns the right content.

Travel t = new Travel();
string x = t["Name"];
    or 
string x = t[Travel.Name];

Answer 6

You could make your life easier by encapsulating your getter and setter logic in a base class and then simply calling those methods from any new properties you create (simply acting as thin wrapper around those methods). Here's an example:

public class Travel : LocalizedRessourceSubscriber
{

    private Ressource<string> Ressource1 = null;
    private Ressource<string> Ressource2 = null;

    public String TravelName { 
        get { return GetRessource<string>(Ressource2); }
        set { SetRessource<string>(Ressource1, value); } 
    }

    public String TravelDescription {
        get { return GetRessource<string>(Ressource2); }
        set { SetRessource<string>(Ressource2, value); } 
    }

}

public class LocalizedRessourceSubscriber
{

    protected T GetRessource<T>(Ressource<T> Source)
    {
        return LocaleHelper.GetRessource<T>(Source);
    }

    protected void SetRessource<T>(Ressource<T> Source, T Value)
    {
       (Source ?? 
           (Source = new Ressource<T>())
                ).DefaultValue = Value;
    }

}

...This way, there is very little logic in your properties and you are repeating less code. This assumes the following classes (which I mocked as genericized):

public static class LocaleHelper
{
    public static T GetRessource<T>(Ressource<T> Source)
    {
        return default(T);
    }
}

public class Ressource<T>
{
    public T DefaultValue { get; set; }
}

Answer 7

That doesn't make sense. using propertys the way you currently have them, you can simply write:

   Travel t = new Travel();
   string tvlName = t.TravelName;    
   string desc = t.TravelDescription;

If you changed to the way you want you'd have to specify the parameter as well

   Travel t = new Travel();
   LocalizedString tvlName = t.TravelName([someresopurcedesignator]);    
   LocalizedString desc = t.TravelDescription([someresopurcedesignator]);  

all you could do is make a "propertyBag" emulator

   public class Travel 
   {
       private LocalizedString props = new LocalizedString();
       public LocalizedString Propertys
       {
          get { return props; }
          set { props = value; }
       }

   }

   public class LocalizedString // this is property Bag emulator
   {
       public string this[string resourceName]
       {
           get{ return LocaleHelper.GetRessource(resourceName); }
           set{ LocaleHelper.GetRessource(resourceName) = value; }
       }
   }

You would access this like this:

   Travel t = new Travel();
   t.Propertys[NameResource1] = "Bob Smith";
   t.Propertys[DescriptionResource2] = "Fun trip to discover the orient";
   string tvlName = t.Propertys[NameResource1];    
   string desc    = t.Propertys[DescriptionResource2];