谁帮我编个c#程序“输入任意一串字母（不分大小写），输出排好序的小写字母形式”谢谢！我初学者！

class Program
{

static void Main(string[] args)
{
Console.WriteLine("In Put Some Chars");

string str = Console.ReadLine();
str = str.ToLower();
string orderStr = OrderStr(str);

Console.WriteLine(orderStr);

}

/// <summary>
/// 排序
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
private static string OrderStr(string str)
{
string orderStr = "";
char[] chars = str.ToCharArray();
for (int i = 0; i < chars.Length; i++)
{
for (int j = i; j < chars.Length; j++)
{
if (chars[i] > chars[j])
{