241.

struct MyStruct
{
      public int x = 10;
      public int y = 30;
}
class MyClient
{
      public static void Main()
      {
            MyStruct ms = new MyStruct();
            int sum = ms.x + ms.y;
            Console.WriteLine("The sum is {0}", sum);
      }
}

It is an error to initialize an instance field in a struct.

'MyStruct.x': cannot have instance field initializers in structs
'MyStruct.y': cannot have instance field initializers in structs