SampleApp.MainForm.focalLengthBox_Leave C# (CSharp) Method

        private void focalLengthBox_Leave(object sender, EventArgs e)
        {
            float value;

            if (float.TryParse(focalLengthBox.Text, NumberStyles.Float, CultureInfo.InvariantCulture, out value))
            {
                focalLength = value;
            }
            else
            {
                focalLengthBox.Text = focalLength.ToString();
                errorProvider.SetError(focalLengthLabel, "Wrong focal length was specified. Restored to previous value.");
            }
        }