查找字符

            Console.WriteLine("请输入字符");
            string a = Console.ReadLine();
            string A=a.ToLower();
            
            Console.WriteLine("请输入您想要查找的字符");
            string b = Console.ReadLine();
            string B=b.ToLower();

            bool c = a.Contains(B);

            int x = a.Length, y = 0, m , n ;

            if (c)
            {                
                for ( m = 0; m < x; m++)                      
                {
                    n = A.IndexOf(B, m);//B是索引值，k是索引的起始位置

                    if ( n == m) 
                    
                        y++;                    
                }
                Console.Write("您输入的字符中包含" + y + "个"+B);              
            }
            else
                Console.Write("您输入的字符中不包含"+ B);
            Console.ReadLine();