C# Validation for specific input

Question

I'm kinda new to this thread, but in short summary i'm having trouble with a small validation issue. Basically, i'm attempting to make a simple validation program that will collect a user's input and then determine if the input is valid in terms of, input being correctly implemented, the number being positive, and the number having to be either 0, 1, 2, 3, 4 or 5.

The overall program runs, but the issue i'm facing is every form of input is deemed an error, thus displaying my error statement, even if it is a valid input like 5 for example. I feel like there is a small mistake,i have made that is causing this, So is there any suggestions?

 int user_input;
 int count = 0;
 do
 {
    Console.Write("\n\nUser Input:"

    if ((int.TryParse(Console.ReadLine(), out user_input) == false)||(user_input < 0 || user_input != 0 ||user_input != 1 || user_input != 2
                || user_input != 3 || user_input != 4 || user_input != 5)) 
    {

       Console.WriteLine("Error : the action entered is not a valid number.");
       count = 0;
    }
    else
       count = 1;

Answer 1

You already got an answer about the problem with predicate logic. But you can even more simplify with linq like:

var count = (new string[]{"1","2","3","4","5"}).Contains(Console.ReadLine()) ? 1 : 0;

Answer 2

Your mistake is because you use OR operator. For example user print 3. In your statements one condition return false (input != 3), but all others return true.. That's why you always go into if condition..

You can use AND operator, but I can recommend you to simplify your condition. It will be more understandable and readable:

var count = 0;
do
{
   Console.Write("\n\nUser Input:");

   int user_input;
   if ((int.TryParse(Console.ReadLine(), out user_input) == false) || (user_input < 0 || user_input > 5))
   {

      Console.WriteLine("Error : the action entered is not a valid number.");
      count = 0;
   }
   else
      count = 1;
} 
while (count != 1);