c# - How can I test a decimal for null? -

i've got code intended convert null decimal vals "zero" value:

decimal paymenttot = tryconverttodecimal(boxpaymentamount.text); if ((null == paymenttot) || (paymenttot < 0)) {     paymenttot = 0m; // or 0? }  private decimal tryconverttodecimal(string incoming) {     decimal result = 0.0m;     try     {         result = convert.todecimal(incoming);     }     catch     {         ; // nada     }     return result; } 

it compiles, warning: "the result of expression 'false' since value of type 'decimal' never equal 'null' of type 'decimal?'"

i don't grok it's trying tell me. sort of test need appease warning emitter and, more importantly, see code can equate 'true' when intent?

decimal value type , can't null.

if want have nullable decimal use nullable<decimal> or decimal? wrapper on decimal type, (it still value type though).

see: nullable<t> structure

you can have method parsing as:

private nullable<decimal> tryconverttodecimal(string incoming) {     nullable<decimal> returnvalue = null;     decimal result;     if (decimal.tryparse(incoming, out result))     {         returnvalue = result;     }     return returnvalue; } 

also better use decimal.tryparse if going ignore exception in parsing.