C# how to check the string in a textbox is what you want it to be

Question

making a rock paper scissors game in C# for college. I want to show message box when the player enters an invalid command (not rock, paper or scissors) . I tryed this but cant get it to work..

        //if player enters wrong command they will 
        //this feedback
        if (textBoxAttack.Text != "rock" || textBoxAttack.Text != "rock" || textBoxAttack.Text != "paper" || textBoxAttack.Text != "Paper" || textBoxAttack.Text != "scissors" || textBoxAttack.Text != "Scissors")
        {
            MessageBox.Show("Not a valid attack"
                           + "\nPlease Enter one of the Following:"
                           + "\nrock"
                           + "\npaper"
                           + "\nscissors");
            textBoxAttack.Text = "";
        }

It works if i just type in one command (eg: if (textBoxAttack.Text != "rock") )

any pointers? Thanks.

Answer 1

Your boolean logic is wrong, because it will always not equal to one of the values, and thus will always be true. Change || to &&, and it should work.

Answer 2

You need && instead of ||.

However, i would prefer this concise and readable approach:

string[] allowed = { "rock", "paper", "scissors" };
if (!allowed.Contains(textBoxAttack.Text, StringComparer.CurrentCultureIgnoreCase))
{ 
    string msg = string.Format("Not a valid attack{0}Please Enter one of the Following:{0}{1}"
        , Environment.NewLine, string.Join(Environment.NewLine, allowed));
    MessageBox.Show(msg);
    textBoxAttack.Text = "";
}

Answer 3

Use an array, it makes your work easier.Also you can use ToLower method to make a case-insensitive check.

var values = new [] { "rock", "paper", "scissors" };

if(!values.Contains(textBoxAttack.Text.ToLower()) 
{
    // invalid value
}

Answer 4

string text = textBoxAttack.Text.ToLowerInvariant();
if (text.Text != "rock" && text.Text != "paper" && text.Text != "scissors")
{
...
}

Use a dropdownlist/radiobuttons instead.

Answer 5

if (textBoxAttack.Text == "rock" || textBoxAttack.Text == "Paper" || textBoxAttack.Text == "Scissors")
{
//..Do What do you want
}
else
{
MessageBox.Show("Not a valid attack"
                           + "\nPlease Enter one of the Following:"
                           + "\nrock"
                           + "\npaper"
                           + "\nscissors");
            textBoxAttack.Text = "";
}

Use Combo Box or 3 Buttons for this kind of problem.

Answer 6

Try to do the same but for example adding ToLower() at the end of each text attribute. This way you will only need to check 3 (rock, paper or scissors) becauuse the iput will be lower case ;)

And for the messageBox try something like this:

string[] message = { "Not a valid attack", "Please Enter one of the Following:", "rock", "paper", "scissors" };

if (textBoxAttack.Text.ToLower() != "rock" && textBoxAttack.Text.ToLower() != "paper" && textBoxAttack.Text.ToLower() != "scissors")
    {
       MessageBox.Show(string.Join("\n", message));
       textBoxAttack.Text = "";
    }