Cannot insert Npgsql syntax

Well I saw this was reported before and got fixed once. But apparently it's back.

I'm using AdoNetAppender with NPgsql. Whenever I insert an x parameter into commandText, it will say that x column doesn't exist. I have tried a variation of :x ?x @x and none seems to work. (:x will say the syntax is error)

For example:

<commandText value="INSERT INTO mylog(columnname) VALUES(@x)" />

<parameter>

<parameterName value="@x">

will say that x doesn't exist.

<commandText value="INSERT INTO mylog(columnname) VALUES(:x)" />

<parameter>

<parameterName value="x">

will say that syntax error near :