can a c# program start with a '{'; if not, why not?

My question, to which the answer is not known to me is stated in the title, i.e.:

can a c# program start with a {; if not, why not?

Everything that follows below details my research & thought process to date:

Note: referencing the "c# Language Specification 5.0";
code compiled with vs2015 community edition.

From §2.2.2 Lexical grammar, this sentence appears to imply that one can start with a { because a { is a token:

"Every source file in a C# program must conform to the input production of the lexical grammar (§2.3)."

§2.4 Tokens include punctuators and { is a punctator [§2.4.5 Operators and punctuators]

However, §9. Namespaces begins "C# programs are organized using namespaces."

§9.1 Compilation units: "A compilation-unit defines the overall structure of a source file."

compilation-unit:

extern-alias-directivesopt using-directivesopt global-attributesopt

namespace-member-declarationsopt

"namespace-member-declarations of each compilation unit of a program contribute members to a single declaration space called the global namespace"

This compiles:

class Program
{
    static void Main(string[] args)
    {
    }
}

This does not compile:

{
    class Program
    {
        static void Main(string[] args)
        {
        }
    }
}

So, although { is a token, it does not contribute a member ... that is possibly why the compiler rejects the beginning {.

However, the namespace-member-declarations are optional ~~ for that reason, perhaps the compiler should allow an intial {.

this is a block:

{
}

not every block must be a something-block, see the last example below.

§1.5 Statements

"A block permits multiple statements to be written in contexts where a single statement is allowed.
A block consists of a list of statements written between the delimiters { and }."

one more example which compiles clean using blocks for scoping:

class Program
{
    static void Main(string[] args)
    {
        {
            System.Int16 integer = System.Int16.MaxValue;
        }
        {
            System.Int32 integer = System.Int32.MaxValue;
        }
    }
}