Hashtable value formating into textbox

I am having trouble displaying a hashtable value into a richtextbox. I want to display a double number as a currency format. double PriceD = Stats["Price"]; // this doesn't work although the type is double, so... string PriceDS = Stats["Price"].ToString(); double PriceD = double.Parse(PriceDS, System.Globalization.NumberStyles.Any); OutputBox.AppendText("Float: {0, 6:C}", PriceD); // this works in console, not textbox // says PriceD has already been declared