c# - How to prevent 'System.FormatException' occurred in mscorlib.dll' with an empty textbox? -


i have programmed simple program me work out amount of carbohydrate per meal (i have diabetes) , issue system.formatexception when 1 of textboxes empty.

how may prevent please ?

my code (using form consisting of 3 textboxes; 2 of require input me , third shows result of simple equation).

public partial class form1 : form {     public form1()     {         initializecomponent();     }      private void form()     {         tbccg.textchanged += textboxchanged;         tbctg.textchanged += textboxchanged;     }       private void textboxchanged(object sender, eventargs e)     {          decimal carbst;         decimal carbsperc = convert.todecimal(tbccg.text);         decimal totcarbs = convert.todecimal(tbctg.text);         carbst = carbsperc / 100 * totcarbs;         tbtc.text = carbst.tostring("###,###.00");     }      }

you can verify text in text boxes

if (string.isnullorwhitespace(tbccg.text))     tbccg.text = "0";  if (string.isnullorwhitespace(tbctg.text))     tbctg.text = "0";  decimal carbsperc = convert.todecimal(tbccg.text); decimal totcarbs = convert.todecimal(tbctg.text);

but if don't have kind of restrictions on text box try using decimal.tryparse.


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