glUniformMatrix4 with count > 1

What is a correct and best way to upload Matrix4[] with a single GL call?

GL class has three versions of UniformMatrix4:

1. Single[] value
2. ref Single value
3. Single* value

I understand that the first version safely fixes the whole array passed to it, but it is not convenient to convert Matrix[] to Single[].

For the second version, I have no idea what really gets fixed and what not. If I pass in ref matrix4array[0].Row0.X, does the whole array really get fixed or not?

Currently I am using the last version, with my own version of UniformMatrix4 that takes in ref Matrix4[] matrix, and which uses fixed (float* matrix_ptr = &matrix[0].Row0.X). I hope this does the right thing, but I wonder if the ref Single value version would work too?

Thanks!