An easy way of doing this is placing your code inside a while loop, so that the code keeps repeating. The only way to exit the loop would be for the condition you just set in the if
clause to be true. So something along the lines of:
class Program
{
static void Main(string[] args)
{
int User;
int Array;
bool isUserWrong = true; //This is a flag that we will use to control the flow of the loop
StreamWriter outfile = new StreamWriter("C://log.txt");
while(isUserWrong)
{
Console.WriteLine("Input an number between 1 and 100");
User = Convert.ToInt32(Console.ReadLine());
if (User < 101 && User > 0)
{
for (Array = 1; Array <= User; Array++)
{
Console.WriteLine(Array + ", " + Array * 10 * Array);
outfile.WriteLine(Array + ", " + Array * 10 * Array);
}
isUserWrong = false; // We signal that we may now leave the loop
}
else
{
Console.WriteLine("Sorry you input an invalid number. ");
Console.ReadLine();
//Note that here we keep the value of the flag 'true' so the loop continues
}
}
Console.WriteLine("Press Enter To Exit The Console");
outfile.Close();
Console.ReadLine();
}
}