While or and not equal to not working?

Question

Im quite new to C# and am trying to write a super simple loop

        while ((var_app_choice != "Exit") || (var_app_choice != "Test"))
        {
            //stuff
        }

I have a console application where an end user will input a value

If this value is not equal (!=) to Exit OR Test then it should loop.

What am i doing wrong here?

Thanks

Solution 1

If you want to come out of the loop, when the User enters Exit or Test then you need the && operator not ||

while ((var_app_choice != "Exit") && (var_app_choice != "Test"))
    {
        var_app_choice = Console.ReadLine();
        //stuff
    }

Solution 2

I think you want and not or...

If the value of var_app_choice is "Test", then the first condition is true and the loop will execute. Similarly, if it's "Exit", then the second condition is true. In other words, you have an infinite loop...

Comments

[Admin]

Here is my answer from a very similar question. It deals with a different implementation (IE conditionals, not C#), but the logic/reasoning is the same ..

[chilly8063]

I think I need more sleep! This is exactly what I was looking for, thanks!

[Habib]

@user1718989, you are welcome, and Welcome to StackOverflow :)

[Jeppe Stig Nielsen]

According to De Morgan's law this can also be written: while (!(var_app_choice == "Exit" || var_app_choice == "Test")) { ... }. The "not" operator ! has been "pulled out", and "and" changed to "or".

[Jeppe Stig Nielsen]

I agree your version is most clear. I just wanted to give another formal expression of "the choice is not Exit or Test".