How to Pass null value byte Field

hi

I am insert the image using byte methods using sp My code below this but following error comes how to solve this
my issue how to pass null value to byte field or how to convert string to byte

my error like this
========================
ex.Message = "Failed to convert parameter value from a String to a Byte[]."


My code like this
====================
if (Session["b"] == null)
{
cmd.Parameters.Add("@StdImagePath", SqlDbType.Image).Value = "";
}

Mark as Answer if its helpful to you

Kumaraspcode2009@gmail.com