Check If A String Value Is Numeric

Introduction

This article will give you a way to determine if a given string has a valid number style (Integer, Float, Currency, etc.) according to specified/current culture.

Background

In all VBScript and Visual Basic applications, there is a built-in function called IsNumeric / IsCurrency, but in C# there is no built-in function with the same functionality.
I have investigated a little and found out that all given solutions always use try catch to find out if the given string value can be parsed.

That seemed like a good way to test it, BUT what if the number contains commas or a currency sign?
Then I have to add another check to this code and strip down the non numeric sign and test the result.
Here I present a simple way that is supported by C#.

The Solution

In the code shown below, I actually use a built-in functionality of C# to determine if a given string value stands up to the requirements I want.

public bool isNumeric(string val, System.Globalization.NumberStyles NumberStyle)
{
    Double result;
    return Double.TryParse(val,NumberStyle,
		System.Globalization.CultureInfo.CurrentCulture,out result);
}

The above function allow me to test if the given string stands up to one or more of the following styles:

• Hex Number
• Number
• Currency
• Float

A more detailed list and explanation regarding System.Globalization.NumberStyles can be found here.

Examples

If you want to test for an integer number, then do the following:

isNumeric("42000", System.Globalization.NumberStyles.Integer)

If you want to test for an integer number separated with commas, then do the following:

isNumeric("42,000", System.Globalization.NumberStyles.Integer | 
	System.Globalization.NumberStyles.AllowThousands)

Using Other Cultures

I use the current culture as shown in the code below.
A list of all available culture names can be obtained here.

public bool isNumeric
    (string val, System.Globalization.NumberStyles NumberStyle, string CultureName)
{
    Double result;
    return Double.TryParse(val,NumberStyle,new System.Globalization.CultureInfo
				(CultureName),out result);
}

There are many ways to approach this problem, I chose the one that suits beginner levels and does not involve any Regular Expression which requires a higher level of expertise.

If you are interested in a solution that involves Regular Expressions, please take a look at the following links:

• Numeric Validation Scripts
• .NET Regular Expressions to validate data

Enjoy and tell me your findings.

History

• 7^th March, 2006: Initial post