Passing DBNull or Decimal value through one method

i'm using , sql stored procedure , command in asp.net app, call method or function value in textbox on page, parse string decimal value , pass on decimal if valid, if null empty didn't populate textbox pass on dbnull.value command parameter , not null.  when pass on null command parameter isn't passed when command executed.  i'm trying save myself writing bunch of if else statements , call method save me time, there several textboxes need conversion with.  appreciated!

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michael duhon

if(string.isnullorempty(textbox.text))     command.parameters.addwithvalue("@param", dbnull.value); else     command.parameters.addwithvalue("@param", decimal.parse(textbox.text));

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