Some Usability Thoughts for the Weekend...

The objective was to give the tool to one of our customers in order to facilitate their work, hence: pay attention to usability factors.
I started with a simple GUI:

So far, nothing special. There is a source folder textbox and a destination folder. They're self-explanatory I guess. What the program should do (for comfortability reasons) is to create the destination folder if it doesn't exist and if it exists already, delete all its content, as it might originate from a previous elaboration.

A naive approach would be to do

if(!Directory.Exists(destinationDir))
{
   Directory.CreateDirectory(destinationDir);
}
else
{
   //delete all files and directories in destinationDir
}

But attention! What might a "dummy" user do what an "expert" user might not? Probably enter something like this:
Source: C:\sourceFileDirectory
Destination: C:\sourceFileDirectory
Bad: You delete all of the source files.

Or even worse:
Source: C:\sourceFileDirectory
Destination: C:\
Bad: You wipe his C drive :D.

These are exactly the problems that are often overlooked (as they might seem obvious) and which then cause enormous damage. Therefore a possible solution might be..

if(!Directory.Exists(destinationDir))
{
   Directory.CreateDirectory(destinationDir);
}
else
{
   //create an output directory inside the specified 
   destinationDir = Path.Combine(destinationDir, "Out");

   if(!Directory.Exists(destinationDir))
   {
      //create it
   }
   else
   {
      //Ask the user about wiping the content of the output directory
      //Do it if confirmed
   }
}