Find minimum and maximum number from array, minimum is always 0

Besides on your problem, you can use Enumerable.Min and Enumerable.Max methods like;

int[] numbers = new int[]{1, 2, 3 ,4};
Console.WriteLine(numbers.Min()); //1
Console.WriteLine(numbers.Max()); //4

Don't forget to add System.Linq namespace.

Your issue is that you're initializing min and max to numbers[0] before numbers is populated, so they're both getting set to zero. This is wrong both for min (in case all your numbers are positive) and for max (in case all your numbers are negative).

If you move the block

int min = numbers[0];
int max = numbers[0];

to after the block

for (int i = 0; i < n; i++)
{
    Console.Write("Enter number {0}:  ", i+1);
    numbers[i] = Convert.ToInt32(Console.ReadLine());
}

then min and max will both be initialized to the first input number, which is fine. In fact you can then restrict your for loop to just check the subsequent numbers:

for (int i = 1; i < n; i++)
    ....

Just make sure the user's value of n is greater than zero!

You are initializing min to 0.

Try following

int min = Int32.MaxValue;

Also In case you are accepting negative values as input, you should initialize max to minimum integer value.

int max = Int32.MinValue;