Csharp program to print Rhombus of numbers:

 int nu = 5;
            for (int i = 1; i <= nu; i++)
            {
                for (int j = 1; j < i; j++)
                {
                    Console.Write(j);
                }
                for (int j = i - 2; j > 0; j--)
                {
                    Console.Write(j);
                }
                Console.WriteLine();
            }

Output :
1
121
12321
1234321