What is the best way to implement dynamic property in a C# object?

Question

I have a number of class objects, each of which needs a URL field which is always formatted in the same way via parameter TypeId, another property of the class.

What is the best way to abstract this as a dynamic property so the URL field is generated based on the TypeId and ItemId properties from the class.

I can think of many ways to do this but wondered what the recommended practice was.

Example below:

public class MyObject
{
    public int Id { get; set; }
    public string URL
    {
        get
        {
            if (TypeId == 3)
            {
                return "/do/this/" + ItemId;
            }
            if (TypeId == 5)
            {
                return "/do/that/" + ItemId;
            }
            return "#";
        }
    }
    public int ItemId { get; set; }
    public int TypeId { get; set; }
}

Do you know all the type IDs, or is that also dynamic? If you know them, this suggests maybe subclassing is appropriate. Or maybe you simply need another class to be a translator. — Anthony Pegram
– Anthony Pegram, Commented Jan 24, 2013 at 16:19
TypeId and ItemId are always set and available when requesting URL. They are obtained from a DB and are dynamic. — Nick
– Nick, Commented Jan 24, 2013 at 16:22

itsme86 · Accepted Answer · 2013-01-24 16:32:01Z

5

You could set up a dictionary with all of the known TypeIds and a Func<int, string> to return the URL. You could even make it so new TypeIds and URL-formatting functions could be added at runtime:

private Dictionary<int, Func<int, string>> _urlFormatters;

public string URL
{
    get { return _urlFormatters[TypeId](ItemId); }
}

// In the constructor or some other init area:
{
    _urlFormatters = new Dictionary<int, Func<int, string>>
        {
            { 3, itemId => "/do/this/" + itemId },
            { 5, itemId => "/do/that/" + itemId }
        };
}

edited Jan 24, 2013 at 16:32

answered Jan 24, 2013 at 16:25

itsme86

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Comments

Cyril Gandon · Accepted Answer · 2013-01-24 16:23:36Z

You can go a step further and implement it full object:

public abstract class MyObject
{
    public int ItemId { get; set; }
    public virtual string URL { get { return "#"; } }
}
public class MyObjectType3 : MyObject
{
    public override string URL { get { return "/do/this/" + ItemId; } }
}
public class MyObjectType5 : MyObject
{
    public override string URL { get { return "/do/that/" + ItemId; } }
}

It depends if you have a lot of type, if this logic make sense or not.
This is just an other solution, but the one you give looks fine also.

qxn · Accepted Answer · 2013-01-24 16:22:38Z

2

abstract class BaseClass {
    public int ItemId { get; set; }
    public abstract string BaseUrl { get; }
    public string Url {
        get {
            return BaseUrl + ItemId;
        }
    }
}

class Type3 : BaseClass {
    public override string BaseUrl {
        get { return "/do/this/"; }
    }
}

class Type5 : BaseClass {
    public override string BaseUrl {
        get { return "/do/that/"; }
    }
}

answered Jan 24, 2013 at 16:22

qxn

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Comments

Z . · Accepted Answer · 2013-01-24 16:22:21Z

0

You can do that in a base class that the other classes inherit from...

answered Jan 24, 2013 at 16:22

Z .

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