using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

public class Test
{
	public int[] intValues;
	
	public static void Main()
	{
		string[] arrayData = { "20", "30", "40" };
		FieldInfo f = typeof(Test).GetField("intValues");
		Type t = f.FieldType.GetElementType();
		Test test = new Test();
		f.SetValue(test, GenericConvert.ChangeArrayType(arrayData, t));
		
		Console.WriteLine("int values: {0}",
            string.Join(", ", test.intValues.Select(v => v.ToString()))
        );
	}
}

public class GenericConvert
{
    public static object ChangeArrayType<S>(IEnumerable<S> a, Type t)
    {
        MethodInfo methodDefinition = typeof(GenericConvert).GetMethod("ChangeArrayTypeGeneric");
        MethodInfo method = methodDefinition.MakeGenericMethod(t, typeof(S));
        return method.Invoke(null, new object[] { a });
    }

    public static T[] ChangeArrayTypeGeneric<T, S>(IEnumerable<S> a)
    {
        return a.Select(x => (T) Convert.ChangeType(x, typeof(T))).ToArray();
    }
}