Is there a way to bridge empty lines with Substring?

Question

With the following code, I delete line by line in a TextBox (0, 39). Now there is on the last place a money amount (1 any Articel 10.00) which I want to deduct from the total amount. For that, I use the Substring. But there I get errors, as probably the empty spaces are not interpreted. Is there a simple solution to this? Thanks

private void btnDelete_Click(object sender, EventArgs e)
{            
    if (TextBox1.Text.Length > 0)            
    {
        txtTotal.Text = (Double.Parse(txtTotal.Text) - Double.Parse(TextBox1.Text.Substring(8, 2))).ToString("0.00");
        TextBox1.Text = TextBox1.Text.Remove(0, 39);               
    }

    if (TextBox1.Text.Length == 0)
    {
        MessageBox.Show("The cart is empty");

Answer 1

Few things you can do to make your life easier (assuming you have to keep a TextBox as you have stated to others.)

Before I get into the details however, the issue seems to be you're having trouble parsing text that represents lines of data, data which contains amounts which you want to act on. If this is an incorrect assumption, disregard this answer.

Ok, back to it...

1. Rather than trying to work with the text directly in the TextBox, start by reading in your entire string as a list of lines (i.e. List<String>). You can do that with the Split function or with RegEx expressions. See here

2. Use RegEx expressions for each line to identify not just the type of line it is (an 'item' line or the 'All' line at the bottom) as well as the various parts of those lines. For instance, you can use a RegEx that starts at the end of the line and goes backwards looking for a number (in the form of a string.) Use the result of that for your Parse method to get the actual numeric value.

Finally, if you still need to remove the lines of text (I'm not sure if you're removing the text just for your logic or if you need to display it) simply remove them from your list of strings for the lines. If it needs to be displayed back in the UI (doubtful as it seems it should be blank at the end of processing) just use Join to convert the lines back to a string, then set that back to the TextBox.Text property.

Hope this helps!

Mark

P.S. To (try and) avoid comments such as the ones you got about your design, it may help to start your question by saying something like 'Unfortunately I'm restricted to using a TextBox due to issues outside of this question, hence I'm looking for an answer here.' At least that should cut back on those responses telling you to 'Do it differently!' instead of answering your question.