CODEWITHSUNDEEP
c#.net
rexdefuror
rexdefuror

Reputation: 583

Limiting class and class properties

Is there a way to limit a class so only 1 property can hold value while rest will have to be null. Or do I have just have to handle it by assigning all others to null when any is set?

Is there any more viable way of approaching this?

Upvotes: 2

Views: 183

Answers (3)

Rodrick Chapman
Rodrick Chapman

Reputation: 5543

The difficulty you're having is that you're trying to use a conjunction (AND) to express a disjunction (OR).

When you have a class with a bunch of properties like

class Foo
{
    public Something        Property1 { get; set; }
    public SomethingElse    Property2 { get; set; }
    public Whatever         Property3 { get; set; }

}

You're saying that Foo is:

Something AND SomethingElse AND Whatever.

But, what you really want to say is that Foo is:

Something OR SomethingElse OR Whatever.

As David Arno mentioned in his answer, ML languages like F# have a compact way of expressing this idea using discriminated unions. But, the larger concept is that of a sum type, which is the way to express the notion of disjunction (i.e. the logical OR) in the type system. C# can also easily express sum types, albeit with a bit more typing than F# (no pun intended).

public class Foo
{
    public Bar Property { get; set; }
}

public abstract class Bar
{
    public class Something : Bar
    {

    }

    public class SomethingElse : Bar
    {

    }

    public class Whatever: Bar
    {

    }
}

Now we have what you want: Objects of type Foo are either a Something or SomethingElse or Whatever, but they can only be one of those things at any given time.

Upvotes: 1

DevEstacion
DevEstacion

Reputation: 1977

you can implement it like this on a class

public class OneProp
{
  private string val1;
  public string Value1 { get { return val1; } };

  private string val2;
  public string Value2 { get { return val2; } };

  public void SetValue(string propName, string propValue)
  {
   // null all values here
   val1 = null;
   val2 = null;

    switch(propName)
    {
      case "Value1":
      val1 = propValue;
      break;

      case "Value2":
      val1 = propValue;
      break;
    }
  }
}

then create an instance of it;

OneProp val = new OneProp();
val.SetValue("name", "value");

You can also do it in the constructor.

Upvotes: 0

David Arno
David Arno

Reputation: 43264

There is no way built in to C# to do this. What you are describing is handled via discriminated unions in F#, but C# doesn't have such types. You could write your own union class to offer such behaviour though.

Upvotes: 4

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