Passing a class property as a parameter

Question

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)

You can replace your whole method with a trivial LINQ query. — SLaks, Sep 27 '11 at 12:53
possible duplicate of [How can I pass a property of a class as a parameter of a method?](http://stackoverflow.com/questions/1178574/how-can-i-pass-a-property-of-a-class-as-a-parameter-of-a-method) — nawfal, Feb 11 '13 at 10:38

score 7 · Accepted Answer · answered Sep 27 '11 at 12:57

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)

Edited code to make the properties public. I'll try your code, and look into Linq. Thx — vowel-house-might, Sep 27 '11 at 13:03

score 0 · Answer 2 · edited May 23 '17 at 12:25

0

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.

edited May 23 '17 at 12:25

Community

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answered Sep 27 '11 at 12:58

mtijn

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Passing a class property as a parameter

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