using System;
public class Program
{
static void HocForeach()
string str = "abcde";
string newCh = "";
string ch = "";
foreach(char c in str)
ch = char.ToUpper(c).ToString();
newCh += ch;
}
Console.WriteLine("Kết quả chuỗi: {0}",newCh);
Console.ReadLine();
public static void Main()
HocForeach();