Question

I’m currently working on a homework assignment where I need to set up a calculator-type program. It needs to read one or two user-input values (depending on the calculation), and then perform the calculation based on the values.

I currently have

• 2 textBoxes (tbInput1 and tbInput2),
• 4 radioButtons,
• one button (btnCalc)
• a blank label in which the result will be displayed.

Two of the radioButtons (rbtnTrap and rbtnFak) disable the first textBox when checked; the other two need two values to be entered, and for that reason enable both textBoxes when checked. btnCalc is supposed to enable itself when the relevant number of textBoxes have value – the relevant number of textBoxes depends on which radio button is checked.

The problem is that when I check rbtnTrap or rbtnFak (disabling tbInput1) and enter an integer in tbInput2, btnCalc stays disabled.

I’ll try to explain what I have so far:

• In the _TextChanged event for tbInput1, I have an exact copy of the second if block posted below. tbInput1 is only active when rbtnPot OR rbtnFib are checked, so that control only runs when that is the case.
• In the _TextChanged event for tbInput2, I have the below, since tbInput2 is always enabled, and the control must run no matter which radio button is checked, although the control should run differently if i check rbtnTrap OR rbtnFak as opposed to rbtnPot OR rbtnFib.

Or that’s my understanding of it. I’m certainly open to suggestions and corrections.

private void tbInput2_TextChanged(object sender, EventArgs e)
{
    //For single-field values
    if ((rbtnTrap.Checked || rbtnFak.Checked) && 
        !string.IsNullOrWhiteSpace(this.tbInput2.Text))
    {
        btnCalc.Enabled = true;
    }
    else
    {
        btnCalc.Enabled = false;
    }
    // For multi-field values
    if ((rbtnPot.Checked || rbtnFib.Checked) && 
        (!string.IsNullOrWhiteSpace(this.tbInput1.Text)
        && !string.IsNullOrWhiteSpace(this.tbInput2.Text)))
    {
        btnCalc.Enabled = true;
    }
    else
    {
        btnCalc.Enabled = false;
    }
}

Answer 1

Because it is a homework, I am not going to give your the straight answer, but instead a hint: the problem is in the code of the tbInput2_TextChanged event (code that you posted).

When rbtnTrap or rbtnFak are checked, your code will be run following such a path you don’t think it will. Set a breakpoint (F9) on the first line of the tbInput2_TextChanged code and run the code step by step (F10) after entering some text in tbInput2.
You will see why your button btnCalc is enabled as you think it is, but disabled in the next moment.

Feel free to comment if you need more help afterwards. 🙂

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EDIT

The problem comes from your if blocks. When one of rbtnTrap and rbtnFak is checked:

• your code will run in the if clause of the first block and then do btnCalc.Enabled = true; but…
• it will also run in the else clause of the second block (because (rbtnPot.Checked || rbtnFib.Checked) is false) and thus do btnCalc.Enabled = false;.