IsNumeric function in c#

Question

I know it's possible to check whether the value of a text box or variable is numeric using try/catch statements, but IsNumeric is so much simpler. One of my current projects requires recovering values from text boxes. Unfortunately, it is written in C#.

I understand that there's a way to enable the Visual Basic IsNumeric function in Visual C# by adding a reference to Visual Basic, though I don't know the syntax for it. What I need is a clear and concise walkthrough for enabling the IsNumeric function in C#. I don't plan on using any other functions indigenous to Visual Basic.

Answer 1

public bool IsNumeric(string value)
{
    return value.All(char.IsNumber);
}

Answer 2

To totally steal from Bill answer you can make an extension method and use some syntactic sugar to help you out.

Create a class file, StringExtensions.cs

Content:

public static class StringExt
{
    public static bool IsNumeric(this string text)
    {
        double test;
        return double.TryParse(text, out test);
    }
}

EDIT: This is for updated C# 7 syntax. Declaring out parameter in-line.

public static class StringExt
{
    public static bool IsNumeric(this string text) => double.TryParse(text, out _);
}

Call method like such:

var text = "I am not a number";
text.IsNumeric()  //<--- returns false

Answer 3

You could make a helper method. Something like:

public bool IsNumeric(string input) {
    int test;
    return int.TryParse(input, out test);
}

Answer 4

It is worth mentioning that one can check the characters in the string against Unicode categories - numbers, uppercase, lowercase, currencies and more. Here are two examples checking for numbers in a string using Linq:

var containsNumbers = s.Any(Char.IsNumber);
var isNumber = s.All(Char.IsNumber);

For clarity, the syntax above is a shorter version of:

var containsNumbers = s.Any(c=>Char.IsNumber(c));
var isNumber = s.All(c=>Char.IsNumber(c));

Link to unicode categories on MSDN:

UnicodeCategory Enumeration

Answer 5

Using C# 7 (.NET Framework 4.6.2) you can write an IsNumeric function as a one-liner:

public bool IsNumeric(string val) => int.TryParse(val, out int result);

Note that the function above will only work for integers (Int32). But you can implement corresponding functions for other numeric data types, like long, double, etc.

Answer 6

http://msdn.microsoft.com/en-us/library/wkze6zky.aspx

menu: Project-->Add Reference

click: assemblies, framework

Put a checkmark on Microsoft.VisualBasic.

Hit OK.

That link is for Visual Studio 2013, you can use the "Other versions" dropdown for different versions of visual studio.

In all cases you need to add a reference to the .NET assembly "Microsoft.VisualBasic".

At the top of your c# file you neeed:

using Microsoft.VisualBasic;

Then you can look at writing the code.

The code would be something like:

   private void btnOK_Click(object sender, EventArgs e)
   {
      if ( Information.IsNumeric(startingbudget) )
      {
         MessageBox.Show("This is a number.");
      }
   }

Answer 7

Try following code snippet.

double myVal = 0;
String myVar = "Not Numeric Type";

if (Double.TryParse(myVar , out myNum)) {
  // it is a number
} else {
  // it is not a number
}

Answer 8

I usually handle things like this with an extension method. Here is one way implemented in a console app:

namespace ConsoleApplication10
{
    class Program
    {
        static void Main(string[] args)
        {
            CheckIfNumeric("A");
            CheckIfNumeric("22");
            CheckIfNumeric("Potato");
            CheckIfNumeric("Q");
            CheckIfNumeric("A&^*^");

            Console.ReadLine();
        }

        private static void CheckIfNumeric(string input)
        {
            if (input.IsNumeric())
            {
                Console.WriteLine(input + " is numeric.");
            }
            else
            {
                Console.WriteLine(input + " is NOT numeric.");
            }
        }
    }

    public static class StringExtensions
    {
        public static bool IsNumeric(this string input)
        {
            return Regex.IsMatch(input, @"^\d+$");
        }
    }
}

Output:

A is NOT numeric.

22 is numeric.

Potato is NOT numeric.

Q is NOT numeric.

A&^*^ is NOT numeric.

Note, here are a few other ways to check for numbers using RegEx.

Answer 9

Tested with Net6 and universal with object because needed in my app:

public static bool IsNumeric(this object text) => double.TryParse(Convert.ToString(text), out _);

Works with null and string.empty and also tested "".

Answer 10

public static bool IsNumeric(string Value)
{
        return decimal.TryParse(Value, out _) || double.TryParse(Value, out _);
        /*
            decimal vs double:

            If a numeric value uses lot of decimal digits, it may not be convertible to 'double' type!
            If a numeric value is too big, it may not be convertible to 'decimal' type!

            Although in recent versions of Visual Studio Core, for number having too many decimal digits, 
            "double.TryParse(Value, out _)" returns "true" (which is not compatible with the conceptual 
            design of "double" type), it may not work in later versions of the compiler.

            Mr. "Jon Skeet" said some years ago:
            The range of a double value is much larger than the range of a decimal.
            0.1 is exactly representable in decimal but not in double, and decimal  
            actually uses a lot more bits for precision than double does.
        */
}

Answer 11

i read all suggested and compare its. this suggeste is better :

public static bool IsNumeric(string value) => double.TryParse(value, out _);

but this solusion is not perfect because is not support float number :

public bool static IsNumeric(string value)=>value.All(char.IsNumber);

Answer 12

Is numeric can be achieved via many ways, but i use my way

public bool IsNumeric(string value)
{
    bool isNumeric = true;
    char[] digits = "0123456789".ToCharArray();
    char[] letters = value.ToCharArray();
    for (int k = 0; k < letters.Length; k++)
    {
        for (int i = 0; i < digits.Length; i++)
        {
            if (letters[k] != digits[i])
            {
                isNumeric = false;
                break;
            }
        }
    }
    return isNumeric;
}