Try 和 catch 块未捕获格式异常

Question

I am trying to catch format exception but the program stops on try block and never reaches to catch block, what is the problem with the code please help me?

private void txtBags_TextChanged(object sender, EventArgs e) 
{
   if (txtBags.Text != "" && PackingBox.Text != "") 
   {
      try 
      {
         txtQty.Text = ((Convert.ToDecimal(txtBags.Text)) * 
         (Convert.ToDecimal(PackingBox.Text)) / 100).ToString();
      } 
      catch (FormatException eX) 
      {
         MessageBox.Show(eX.Message);
      }
   } 
   else 
   {
      txtQty.Text = "";
   }
}

I want to catch the exception and show the message to the user? please tell me how can I do that?

Answer 1

Why handle the exception at all? Why not just avoid it altogether by using TryParse ?:

if (!string.IsNullOrEmpy(txtBags.Text) && !string.IsNullOrEmpty(PackingBox.Text))
{
    if (!Decimal.TryParse(txtBags.Text, out var bags))
    {
        // handle parse failure
        return;
    }

    if (!Decimal.TryParse(PackingBox.Text, out var packingBox))
    {
        // handle parse failure
        return;
    }

    txtQty.Text = (bags * packingBox / 100).ToString();
}

If you're not building with Roslyn/are using an older version of C#, you might need to define the variable beforehand:

decimal bags;
if (!Decimal.TryParse(txtBags.Text, out bags))

And then the same with PackingBox, of course.