input: 
  def convert_program_to_csharp(python_code: str) -> str:
      """ Convert a given Python program to a C# program.
      >>> convert_program_to_csharp("""
      ... def power(x, y):
      ...     if y == 0:
      ...         return 1
      ...     else:
      ...         return x * power(x, y - 1)
      ... """)
      'public int Power(int x, int y)\n{\n    if (y == 0)\n    {\n        return 1;\n    }\n    else\n    {\n        return x * Power(x, y - 1);\n    }\n}\n'
      """
  
output:     csharp_code = ""
      lines = python_code.strip().split('\n')
      indent_level = 0
  
      for line in lines:
          line = line.rstrip()
          if line.endswith(':'):
              csharp_code += ' ' * indent_level + line[:-1].replace('def ', 'public ').replace('(', '(').replace(')', ')') + '\n'
              csharp_code += ' ' * indent_level + '{\n'
              indent_level += 4
          else:
              if line.strip().startswith('return '):
                  line = line.replace('return ', 'return ')
              csharp_code += ' ' * indent_level + line.replace('elif ', 'else if ').replace('else:', 'else') + ';\n'
  
      csharp_code += ' ' * (indent_level - 4) + '}\n'
      return csharp_code