Before you develop your C# Program, it is suggest that you plan first. Plan here means :
- What kind of interface you wanna do
- how your program process
- what need to put in main form, what need to put in class method
- So on…
For small program yes, you will not see the important of this thing. But for large programmed, it is important in order to save your time for develop and correction.
My suggestion, you write all of the planning in a peace of paper before do your programming.