如何从对象列表中获取一个属性的数组？

Question

I have a List of Objects

List<Flywheel> parts1 = new List<Flywheel>();

i want to extract an array of one of the properties.

 parts1 = parts.DistinctBy(Flywheel => Flywheel.FW_DMF_or_Solid).OrderBy(Flywheel => Flywheel.FW_DMF_or_Solid).ToList();

 string[] mydata = ((IEnumerable)parts1).Cast<Flywheel>()
                              .Select(x => x.ToString())
                              .ToArray();

the code for DistinctBy()

public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
    {
        HashSet<TKey> seenKeys = new HashSet<TKey>();
        foreach (TSource element in source)
        {
            if (seenKeys.Add(keySelector(element)))
            {
                yield return element;
            }
        }
    }

what i get in my code is a array of string thart each of them is "XXX.Flywheels.Flywheel" but i need to get the actual values.

Answer 1

This should work:

List<Flywheel> parts1 = new List<Flywheel>();
var mydata = parts1.Select(x => x.FW_DMF_or_Solid).OrderBy(x => x).Distinct().ToArray();

Answer 2

Your ToString() operator is outputting "XXX.Flywheels.Flywheel". You need

string[] mydata = ((IEnumerable)parts1).Cast<Flywheel>()
                          .Select(x => x.FW_DMF_or_Solid.ToString())
                          .ToArray();

Also, you should be able to replace your DistinctBy code with

public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
    return source.GroupBy(x => keySelector(x)).Select(g => g.First());
}

Answer 3

string[] arrayOfSingleProperty = 
         listOfObjects
        .Select(o => o.FW_DMF_or_Solid)
        .OrderBy(o =>o)
        .Distinct()
        .ToArray();