Regex for decimal number validation in C#

Question

I need regular expression which allows positive as well as negative range decimals values

like .89 , -1000 , 0.00 , 0 , 300 , .....

My regex is ^\\d*\\.?\\d*

Problem is that when you entered special characters like $ , ! , * then it accepts those characters.

Answer 1

Instead of regex, I would parse it with decimal.Parse with AllowDecimalPoint and AllowLeadingSign styles and a culture that has . as a NumberDecimalSeparator like InvariantCulture .

var d = decimal.Parse("-.89", 
                      NumberStyles.AllowDecimalPoint | NumberStyles.AllowLeadingSign, 
                      CultureInfo.InvariantCulture);

This captures all needs you mentioned.

Answer 2

You missed a backslash! A single dot has a different meaning in Regex expressions.

public static bool IsValidDecimal()
{
    string input = "132456789"
    Match m = Regex.Match(input, @"^-?\d*\.?\d+");
    return m.Success && m.Value != "";
}

Answer 3

If you are keen on using regex , the following will do:

^-?[0-9]*\.?[0-9]+$

See live demo