CODEWITHSUNDEEP
c#genericsparametersproperties
vowel-house-might
vowel-house-might

Reputation: 1726

Passing a class property as a parameter

I'd like to pass a class property (or a getter/setter if need be) reference to a function.

For example I have an array of a class with lots of boolean flags.

class Flags
{
  public bool a;
  public bool b;
  public bool c;
  public string name;

  public Flags(bool a, bool b, bool c, string name)
  {
    this.a = a;
    this.b = b;
    this.c = c;
    this.name = name;
  }
}

I can write a method that returns all instances of Flags for which a chosen flag is true

public Flags[] getAllWhereAisTrue(Flags[] array)
{
  List<Flags> resultList = new List<Flags>();
  for (int i = 0; i < array.Length; i++)
  {
    if (array[i].a == true) // for each Flags for which a is true
    {                       // add it to the results list
      resultList.Add(array[i]);
    }
  }
  return resultList.ToArray(); //return the results list as an array
}

What would I use to allow me to pass a class property as a parameter, so as to save me from having to write this method once for each boolean property of Flags (in this example that's three times, once for a, b and c)?

I'm trying to avoid giving Flags an array of Booleans in an attempt to keep the resulting code easy to read. I'm writing a library for use by relatively inexperienced coders.

Thank you

(With apologies if this is a dupe of Passing property as parameter in method, I can't quite tell if it's the same issue)

Upvotes: 6

Views: 7661

Answers (2)

mtijn
mtijn

Reputation: 3678

according to the language spec it is not possible to pass properties as ref parameters. this stackoverflow post is on the same subject. moreover, I'll second the comment of SLaks: LINQ has a method that does just this.

Upvotes: 0

BrokenGlass
BrokenGlass

Reputation: 160852

You could use a Func<Flags, bool> as parameter:

public Flags[] getAllWhereAisTrue(Flags[] array, Func<Flags, bool> propertySelector)
{
    List<Flags> resultList = new List<Flags>();
    for (int i = 0; i < array.Length; i++)
    {
        if (propertySelector(array[i])) // for each Flags for which a is true
        {                       // add it to the results list
            resultList.Add(array[i]);
        }
    }
    return resultList.ToArray(); //return the results list as an array
}

Then you could use it like this: 

var allAFlagsSet = getAllWhereAisTrue(flagsArray, x=> x.a);

But really you should not reinvent this - Linq does this out of the box (notice the similarity):

var allAFlagsSet = flagsArray.Where(x=> x.a).ToArray();

Both solutions would require the a,b,c to be public (should really be a public property in this case)

Upvotes: 7

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