c# fix rounding errors in list code example

Example: C# .net core convert to int round up

// Use Math.Ceiling to round up
Math.Ceiling(0.5); // 1

// Use Math.Round to just round
Math.Round(0.5, MidpointRounding.AwayFromZero); // 1

// And Math.Floor to round down
Math.Floor(0.5); // 0