C＃：两步文本框计算仅在两次单击“计算”按钮时才产生正确的结果

Question

I understand exactly why this is happening, but I can't figure out how to fix it. Textbox3 is pulling the initial value of textbox2, not the new calculated value. This is not a school project, rather a simple calculator for my office for some radio hardware we use. I could fix this by making the button click twice programmatically etc, but I want to know how to fix this the correct way. My programs are always so simple I get accused of it being "homework" but I can guarantee it is not. I am sure it is simple as a couple paranthesies missing...Thanks in advance

    private void button1_Click(object sender, EventArgs e)
    {
        if (double.TryParse(textBox1.Text, out origin)
            && double.TryParse(textBox2.Text, out tb2)
             && double.TryParse(textBox4.Text, out channels))

            textBox2.Text = (30.00 - (10 * Math.Log10(origin))).ToString("n2");
            textBox3.Text = (tb2 - (10 * Math.Log10(channels))).ToString("n2");          

    }

Answer 1

Change the calculation to:

tb2 = 30.00 - (10 * Math.Log10(origin));
var tb3 = tb2 - (10 * Math.Log10(channels));
textBox2.Text = tb2.ToString("n2");
textBox3.Text = tb3.ToString("n2");

Answer 2

You are assigning tb2 before you change the value in textbox2. You should change the code to:

            if (double.TryParse(textBox1.Text, out origin)
         && double.TryParse(textBox4.Text, out channels))
        {
            textBox2.Text = (30.00 - (10 * Math.Log10(origin))).ToString("n2");
            if (double.TryParse(textBox2.Text, out tb2)
            {
                textBox3.Text = (tb2 - (10 * Math.Log10(channels))).ToString("n2");
            }
        }