CODEWITHSUNDEEP
c#boolean
FeliceM
FeliceM

Reputation: 4219

Bool test on a string gives unexpected result

This should be self explanatory. I am trying to detect if the first char of the string foo is a negative sign '-'. This is just a test code to test it.

 private void button1_Click(object sender, EventArgs e)
    {
        string foo = textBox1.Text;
        bool negativeValue = foo[1]==('-');
        //bool negativeValue = foo[1].Equals ('-');

        if (negativeValue == true)
        {
            label1.Text = "First char is negative !";
        }

        else if (negativeValue == false)
        {
            label1.Text = "First char is not negative !";
        }
    }

The result is always false even if the first char in the text box is '-'. Why?

Upvotes: 0

Views: 85

Answers (2)

Chris Sinclair
Chris Sinclair

Reputation: 23208

Index lookup in C# is zero-based. So you should call:

foo[0] == ('-')

Using 1 will lookup the second character.

EDIT: Also as an alternative (and perhaps more clear) you can always use:

foo.StartsWith("-")

That should work no matter how inebriated you are. :)

(Also, consider trimming the text input if you want to avoid excessive/accidental preceding spaces from user input)

Upvotes: 3

Anirudha
Anirudha

Reputation: 32827

You are using wrong index.With 1 you are actually referring to 2nd character

Use 0

 bool negativeValue = foo[0]==('-');

Upvotes: 2

Related Questions