Question

Does anyone know how to write a code that allows the user enters a valid decimal value for the length.

Answer 1

example on c #:
Create a new project windows forms application, add the edit and button components to the form, then declare the variable x of the real type, double click on the button component, go to the code editor and write the code: x = Convert.ToString (edit1.text). So, you take the value of the variable from the edit component and do what you need.