Question

I have a string “-4.00 %” which I need to convert to a decimal so that I can declare it as a variable and use it later. The string itself is found in string[] rows. My code is as follows:

foreach (string[] row in rows)
{
string row1 = row[0].ToString();
Match rownum = Regex.Match(row1.ToString(), @"\-?\d+\.+?\d+[^%]");
string act = Convert.ToString(rownum); //wouldn't convert match to decimal
decimal actual = Convert.ToDecimal(act);
textBox1.Text = (actual.ToString());
}

This results in “Input string was not in a correct format.” Any ideas?

Thanks.

Answer 1

Here’s a modified version of your code that changes the regex to use a capturing group and explicitly look for a %. As a consequence, this also simplifies the parsing to decimal (no longer need an intermediary string):

EDIT : check rownum.Success as per executor’s suggestion in comments

string[] rows = new [] {"abc -4.01%", "def 6.45%", "monkey" };

foreach (string row in rows)
{
    //regex captures number but not %
    Match rownum = Regex.Match(row.ToString(), @"(\-?\d+\.+?\d+)%");

    //check for match
    if(!rownum.Success) continue;

    //get value of first (and only) capture
    string capture = rownum.Groups[1].Value;

    //convert to decimal
    decimal actual = decimal.Parse(capture);

    //TODO: do something with actual
}