Question

I have a function that filters objects of a specific class by a chosen field. The way I currently do this is that I pass a string naming the field as an argument to the function. Ideally I would want to be able to use this string to select the field in the object, similar to a dictionary (this functionality exists in javascript for example).

So I have the function (cut down to the relevant bits) here:

private List<HangingArtBundle> ConstrainBundlesBy(List<HangingArtBundle> bundles, string valueString, string constraint)
{
    List<HangingArtBundle> retBundles = new List<HangingArtBundle>();
    List<string> values = new List<string>(valueString.Split(new char[] { '|' }));

    foreach (HangingArtBundle bundle in bundles)
    {
        if (values.Contains(ConstrainedField(constraint, bundle)))
        {
            retBundles.Add(bundle);
        }
    }

    return retBundles;
}

I would like to be able to replace the ConstrainedField(constraint, bundle) part with something like bundle[constraint], where constraint is the name of a field of the class HangingArtBundle. Instead, I have to use this function below, which requires me to manually add field names as needed:

private string ConstrainedField(string field, HangingArtBundle bundle)
{
    if (field.Equals("Category"))
    {
        return bundle.Category;
    }
    else if (field.Equals("AUToolTab"))
    {
        return bundle.AUToolTab;
    }
    else
    {
        return "";
    }
}

If it helps at all, here is the class (essentially just a struct):

public class HangingArtBundle
{
    public string CP { get; set; }
    public string Title { get; set; }
    public string Category { get; set; }
    public string AUToolTab { get; set; }
    public List<HangingArtEntry> Art { get; set; }
}

Is this possible to do in an elegant way in C#?

Answer 1

You can use System.Reflection for this

 private string GetField(HangingArtBundle hab, string property)
 {
    return (string)hab.GetType().GetProperty(property).GetValue(hab, null);
 }

Or perhaps an Extension method to make life a bit easier:

    public static class Extensions
    {
        public static string GetField(this HangingArtBundle hab, string property)
        {
            if (hab.GetType().GetProperties().Any(p => p.Name.Equals(property)))
            {
                return (string)hab.GetType().GetProperty(property).GetValue(hab, null);
            }
            return string.Empty;
        }
    }

Usage:

  string result = bundle.GetField("CP");