https://stackoverflow.com/questions/47781469/linq-select-property-by-name

stack.47781469.cs

void Main()
{
	var listOfPersons = new List<Person>
	{
		new Person(){Id = 1, FirstName = "John", LastName = "Doe", CountryName = "UK", City = "London" },
		new Person(){Id = 2, FirstName = "Jane", LastName = "Doe", CountryName = "UK", City = "Manchester" },
		new Person(){Id = 3, FirstName = "Jim", LastName = "Boe", CountryName = "UK", City = "Brighton" },
		new Person(){Id = 4, FirstName = "Jack", LastName = "Dob", CountryName = "UK", City = "London" },
	};

	listOfPersons
		.Query(p => p.Id)
		.Dump("ids");
	
	listOfPersons
		.Query(p => p.FirstName)
		.Dump("names");
		
	listOfPersons
		.Query("cityName")
		.Dump("cities");
}

public class Person
{
	public int Id { get; set; }
	public string City { get; set; }
	public string CountryName { get; set; }
	public string FirstName { get; set; }
	public string LastName { get; set; }
}

public static class Extensions
{
	public static List<T> Query<T>(this IEnumerable<Person> instance, Func<Person, T> selector)
	{
		return instance
			.Select(selector)
			.Distinct()
			.OrderBy(x => x)
			.ToList();
	}

	public static List<string> Query(this IEnumerable<Person> instance, string property)
	{
		switch (property)
		{
			case "ids": return instance.Query(p => p.Id.ToString());
			case "firstName": return instance.Query(p => p.FirstName);
			case "lastName": return instance.Query(p => p.LastName);
			case "countryName": return instance.Query(p => p.CountryName);
			case "cityName": return instance.Query(p => p.City);
			default: throw new Exception($"{property} is not supported");
		}
	}
}