How to format a decimal value WITHOUT rounding to store into nullable decimal Variable in c# -

i have tried format(truncate) decimal value 4 decimal places. example, want convert decimal numbers like

31.818181818181818181818181818m  or 31.818181818181818181m or 31.81818m  

to

31.8181  

(not rounding 31.8182) , store in nullable decimal variable. have tried following decimal formatting without rounding .net , stop rounding in c# @ number no luck nullable decimals.

here code

private decimal? returnnullabledecimal(decimal? initvalue) {         //e.g. initvalue = 35m;         initvalue = 35m; //just debug;          decimal? outputvalue = null;           if (initvalue != null)             outputvalue = initvalue / (decimal)1.10;         //now outputvalue 31.818181818181818181818181818m         outputvalue = convert.todecimal(string.format("{0:0.0000}", outputvalue)); // <- should 31.8181 gives 31.8182          return outputvalue;     } 

can please help?

any decimal can implicitly converted decimal?, same code works in other example of truncating. if input decimal?, you'll have check null there.

private decimal? returnnullabledecimal(decimal? initvalue) {     if (initvalue.hasvalue)         return math.truncate(10000 * initvalue.value) / 10000;     else         return null; }