Detailed explanation of the use of type parameters in C#

static void InsertA(int aid, string contentXml)
{
//ConnString is a connection string, which requires additional definition
    using (SqlConnection conn = new SqlConnection(ConnString))
    {
        ();
        string sql = "INSERT INTO [A] ([ID],[Content])VALUES(@id,@content)";
        using (SqlCommand comm = new SqlCommand(sql, conn))
        {
            using (XmlTextReader rdr = new XmlTextReader(contentXml, , null))
            {
                SqlXml sqlXml = new SqlXml(rdr);

                SqlParameter parmID = new SqlParameter("@id", aid);
                SqlParameter parmContent = new SqlParameter("@content", , );
                = sqlXml;

                (parmID);
                (parmContent);
                ();
            }
        }
        ();
    }
}