Why can't you declare a static struct in C#, but they can have static methods?

Question

// OK
struct MyStruct
{
    static void Foo() { }
}

// Error
static struct MyStruct
{
}

Answer 1

The key point here is that the static modifier on a class enforces (among other things) that an instance of the class cannot be created. This is done by forcing a private constructor.

The CLR doesn't have any way to prevent an instance of a struct type from being created. Even if there is no public default constructor, simply declaring

struct S { }

S[] items = new S[]{1};

would create an instance of the struct with all of the associated memory set to zero bits.

Note that this is different from a reference type (class), where the same code would create a reference of the specified type (referencing no object aka null) but not an instance of the object itself.