Write a program in C# and ask the user to enter 5 unique numbers

Question

Write a program and ask the user to enter 5 numbers. If a number has been previously entered, display an error message and ask the user to retry. Once the user successfully enters 5 unique numbers, sort them and display the result on the console.

Can anybody please help me on this one? I'm really confused on how to solve this. Here's my code:

var number = new int[5];
Console.WriteLine("Enter 5 unique numbers");

for (int i = 0; i < 5; i++)
{
    number[i] = Convert.ToInt32(Console.ReadLine());
    var numberValue = number[i];

    var currentNumber = Array.IndexOf(number, numberValue);
    if (number[i] == number[0])
    {
        continue;
    }
    else
    {
        if (!(currentNumber == number[i]))
        {
            continue;
        }
        else
        {
            Console.WriteLine("Hold on, you already entered that number. Try again.");
        }
    }

    /* foreach (var n in number) { ... } */
    continue;
}

Array.Sort(number);
Console.WriteLine();

foreach (var n in number)
    Console.WriteLine(n);

Console.WriteLine();

I can't find the solution on the checking if there is already the same number input. Help me please. And please explain why it is the answer.

PS: Can you please only use simple code and do not use keywords like HashSet? I know that will solve the problem but I don't know it yet. I'm just trying to learn C# step by step so I'm sorry for that.. Thank you!

Answer 1

        var number = new int[5];
        Console.WriteLine("Enter 5 unique numbers");

        for (int i = 0; i < 5; i++)
        {
            while (true)
            {
                var newValue = Convert.ToInt32(Console.ReadLine());
                var currentNumber = Array.IndexOf(number, newValue);
                if (currentNumber == -1)
                {
                    number[i] = newValue; // Accept New value
                    break;
                }
                Console.WriteLine("Hold on, you already entered that number. Try again.");
            }
        }

        Array.Sort(number);
        Console.WriteLine();

        foreach (var n in number)
            Console.WriteLine(n);

        Console.ReadLine();

Array.IndexOf() returns index of numberValue in array, or -1 if it does not exist.