Ternary operator usage

Question

Whats wrong with this seemingly straightforward code?

invoice.GST > gstValue ? invoice.GST -= gstValue : invoice.GST = 0;

VS complains
Only assignment, call, increment, decrement, and new object expressions can be used as a statement

Answer 1

Try this:

invoice.GST = ((invoice.GST>gstValue)?(invoice.GST - gstValue):0);