Question

I am trying to insert textbox1 + textbox2 = textbox3. And all my textboxes are set to selectAll(); while entering into textbox. So when I entered to textbox1 all the text will be in select mode and if I click backspace all data will be removed and an error occurring like

Input string was not in correct format

My code is

textBox3.Text = (int.Parse(textBox1.Text) + int.Parse(textBox2.Text)).ToString();`

I tried like

       if (textBox1.Text != "")
        {
            textBox3.Text = (int.Parse(textBox1.Text) + int.Parse(textBox2.Text)).ToString();
        }

In this case The value in the Textbox three is not changing when I click backspace. Means textbox will be null. That’s why value is not changing in thired textbox. Please help me. How could I ovecome this problem?

Answer 1

You are assuming that your inputs (textBox1.Text and textBox2.Text) are integers.

If they are not, int.Parse will fail and give you the error you are seeing.

You need to use int.TryParse:

int result1 = 0:
int.TryParse(textBox1.Text, out result1);
int result2 = 0:
int.TryParse(textBox2.Text, out result2);

textBox3.Text = (result1 + result2).ToString():