Extract decimal from start of string

Question

I have a string like 5.5kg or 7.90gram and I want to get 5.5 or 7.90 as a decimal value. How can I get such result in C# and one more thing that my string will always starts with decimal.

Here is my code that throws an error whenever it will encounter anything except a decimal.

string weight = attributeValue;
if (!string.IsNullOrEmpty(weight))
{
    product.Weight = Convert.ToDecimal(attributeValue);
}
else
{
    product.Weight = 0.00m;
}

Answer 1

I would create a regular expression matching the leading number part. This will partly depend on whether you will always have a decimal point, whether you want to allow commas for thousands separators, whether it will always use . as the decimal point, etc. It might look something like this though:

^-?\d+(?:\.\d+)?

Then match that regular expression against your text, take the value of the match (if it's successful) and use decimal.Parse or double.Parse on that value:

Regex regex = new Regex(@"^-?\d+(?:\.\d+)?");
Match match = regex.Match(text);
if (match.Success)
{
    weight = decimal.Parse(match.Value, CultureInfo.InvariantCulture);
}

Note that for "natural" values such as mass, you may be better off with double than decimal. The latter is more appropriate for "artificial" values such as currency, which are naturally best expressed in decimal and have exact values. It depends on what you're doing though.

Answer 2

here is a completely different approach

    string oldstr = "1.7meter";
        Char[] strarr = oldstr.ToCharArray().Where(c => Char.IsDigit(c) || Char.IsPunctuation(c)).ToArray();
        decimal number = Convert.ToDecimal( new string(strarr));