C# How to access static field of a public struct

Question

I am trying to access a static field of the struct which I already defined as public. However, I still got "inaccessible due to its protection level" Can anyone help me?

public class Program
{
    public struct AT_CMD
    {
        static int x = 7;
       static  byte[] cmd_mode = new byte[3] { 0x2B, 0x2B, 0x2B };
       static  byte[] end_device_assoc = new byte[4] { 0x41, 0x54, 0x41, 0x31 };
      //should be 0 for end device, default is 0
       static  byte[] data_rate = new byte[4] { 0x41, 0x54, 0x42, 0x44 }; //3 for 9600, 5 for 38400
       static  byte[] channel = new byte[4] { 0x41, 0x54, 0x43, 0x48 }; //0x0B-0x1A
       static  byte[] Dest_addr_high = new byte[4] { 0x41, 0x54, 0x44, 0x48 }; //0 FOR 16bit
       static  byte[] Dest_addr_low = new byte[4] { 0x41, 0x54, 0x44, 0x4C };
       static  byte[] my_addr = new byte[4] { 0x41, 0x54, 0x4D, 0x59 }; // 0-0xFFFF
       static  byte[] carriage_return = new byte[1] { 0x0D };
   }  

    static void Main()
    {
        int y = AT_CMD.x;
    }
}

Answer 1

Change it to:

  public struct AT_CMD
  {
        public static int x = 7;

        // ...
  }  

Just making a struct public doesn't affect its members, the members of the struct will be private by default unless you specify otherwise.

UPDATE: Addressing the confusion on default access, internal is the default access for the struct or class itself if declared at the namespace level (not nested in another class/struct):

Classes and structs that are declared directly within a namespace (in other words, that are not nested within other classes or structs) can be either public or internal. Internal is the default if no access modifier is specified.

Whereas, the fields in a class or struct always default to private:

The access level for class members and struct members, including nested classes and structs, is private by default.

From the MSDN.

Answer 2

By default fields are private. Add the most limiting modifier that will still allow you to work with the structure.

public struct AT_CMD
{
    public static int x = 7;
}  

static void Main()
{
    int y = AT_CMD.x;
}

Answer 3

The struct is public, but the members are not.