Error Formatting textbox in C#

Question

I have an error message when I type a number in a textbox to give it a format. when I'm typing with this code :

private void textBoxX1_TextChanged(object sender, EventArgs e)
    {
        textBoxX1.Text = string.Format("{0:F}",double.Parse(textBoxX1.Text));
        string txtval = textBoxX1.Text;

      }

I only want two decimals for formatting so if I type 100 the textbox format it to 100.00 . and then passes that value to the variable txtval but give me this error:

Input string was not in a correct format.

Answer 1

我建议使用TryParse而不是Parse来避免发生异常。

Answer 2

You should use TryParse to first verify if you can parse what's in the textbox. You're getting this exception because the value in the textbox can't be parsed to a double. You should modify your code to look like this :

private void textBoxX1_TextChanged(object sender, TextChangedEventArgs e)
{
    double value = 0.00;

    if (double.TryParse(textBoxX1.Text, out value))
    {
        textBoxX1.Text = string.Format("{0:F}", value);
        string txtval = value.ToString();
    }       
}

What this does is first verify that the value in the textbox can be parsed to a double and then format it and add it to the textbox.