calling getpaymentamount into my gui.

Question

Well it is apparent i am new to c# cause i am having a problem calling a GetPaymentAmount into my GUI.

This is my interface:
namespace Invoice
{
    public interface IPaytable
    {
        decimal GetPaymentAmount();
    }
}
This is my method
public decimal GetPaymentAmount()
        {

               return priceper * quantity;

            }
and i am completely lost as how to make it to where i can display the information from the getpaymentamount into my Results textbox as such:
restxtbx.Text += "Total for this transaction is :$" + WHAT GOES HERE? ;

Steven · Answer

ok actually i needed to add another class and then add in the call to my gui then do what you said. Thanks alot for your help

Alan · Answer

This is what you need: restxtbx.Text += Total for this transaction is :$ + GetPaymentAmount().ToString(); GetPaymentAmount() produces a decimal result which you then have to convert to a string to be able to add it to the first part of the line. The whole string is then added to what's already in the TextBox because of the += operator.