Calculating Integer Percentage

Cast to double first so it doesn't compute a division between integers:

int totalProgress = (int)((double)FilesProcessed / TotalFilesToProcess * 100);

int FilesProcessed = 42;
int TotalFilesToProcess = 153;
int TotalProgress = FilesProcessed * 100 / TotalFilesToProcess;

Console.WriteLine(TotalProgress);

https://dotnetfiddle.net/3GNlVd

If you want to be more accuracy, you can use:

int TotalProgress = Convert.ToInt32(Math.Round(((decimal)FilesProcessed / TotalFilesToProcess) * 100, 0));

If the numbers are greater you will have a difference. For example

int FilesProcessed = 42;
int TotalFilesToProcess = 1530;

The result with decimals will be: 2.74%, if you use the previous methods, you would find 2%, with the formula I am proposing you will obtain 3%. The last option has more accuracy.