using System;
using System.Linq;
using System.Collections;
using System.ComponentModel;

public class Program
{
    public static void Main()
    {
        var args = new string[] { "20", "40", "69" };

        // var value = ConvertObjectsToArray<int[]>(args);

        var dummy = new float[1];
        var array = ConvertObjectsToArray(dummy.GetType(), args);

        Console.WriteLine(array);
    }

    private static IList ConvertObjectsToArray(Type arrayType, string[] args)
    {
        if (!arrayType.GetInterfaces().Contains(typeof(IList)))
            return null;

        IList arrayInstance = (IList)Activator.CreateInstance(arrayType, args.Length);
        Type elementType = arrayType.GetElementType();
        TypeConverter typeConverter = TypeDescriptor.GetConverter(elementType);

        for (int i = 0; i < args.Length; i++)
            arrayInstance[i] = typeConverter.ConvertFromString(args[i]);

        return arrayInstance;
    }

    private static T ConvertObjectsToArray<T>(string[] args) where T : IList
    {
        Type arrayType = typeof(T);
        T arrayInstance = (T)Activator.CreateInstance(arrayType, args.Length);
        Type elementType = arrayType.GetElementType();
        TypeConverter typeConverter = TypeDescriptor.GetConverter(elementType);

        for (int i = 0; i < args.Length; i++)
            arrayInstance[i] = typeConverter.ConvertFromString(args[i]);

        return arrayInstance;
    }
}