There is a pre-defined marketing template, and the relevant part of the template looks like this:
Hi [%first_name | Dear Fan%], xxxxxx
There are so many different syntax for sendgrid template variable substitution out there, it's just very confusing. For example, I've seen [%variable_name%], {{variable_name}}, -variable_name- and <%variable_name%>
how do I pass substitution/personalization/template data (just to list the different names I've seen that appears to refer to the same thing) from the C# client to the template?