How to check if string is number (IsNumeric) in C#?


I have a string "123" and another string "Test", now I want to identify from which you these string conatins number, so How can i check if string is a number or not in C#, is there any method in C# or we need to create custom method for it?

Example :

"11" = true

"Hello"= false


Asked by:- bhanu
2
: 8913 At:- 5/1/2020 7:33:54 AM
C# IsNumeric C#







3 Answers
profileImage Answered by:- vikas_jk

Yes, you can do it using TryParse in C# 7 or above

int n;
bool isNumeric = int.TryParse("11", out n);
Console.WriteLine(isNumeric);

OR

Check if string is Numeric using Regular expression

var RegexCheck=Regex.IsMatch("11", @"^\d+$");
Console.WriteLine(RegexCheck);

OR

Create a Custom Method

public static bool IsNumeric(this string s)
    {
        float output;
        return float.TryParse(s, out output);
    }

Here is the Complete C# Console example

using System;
using System.Text.RegularExpressions;
					
public static class Program
{
	public static void Main()
	{
		int n;
        bool isNumeric = int.TryParse("11", out n);
		Console.WriteLine(isNumeric);
		
		//using Regular Expression
		var RegexCheck=Regex.IsMatch("11", @"^\d+$");
		Console.WriteLine(RegexCheck);
		
		//Using Custom Method
		Console.WriteLine(IsNumeric("Test"));
		Console.WriteLine(IsNumeric("11.3"));
	}
	public static bool IsNumeric(this string s)
    {
        float output;
        return float.TryParse(s, out output);
    }
}

Output:

True
True
False
True

You can try it here: https://dotnetfiddle.net/YZMP4w

Hope it helps.

2
At:- 5/1/2020 8:00:52 AM
I tried the first way "bool isNumeric = int.TryParse("11", out n);" and it works for me, thanks 0
By : bhanu - at :- 5/20/2020 7:30:36 AM
great answer with proper details and fiddle sample, thanks 0
By : pika - at :- 6/3/2022 7:56:44 AM


profileImage Answered by:- bhanu

Above solution works as needed but I would like to add another method, which works best for only numbers (no decimal or currency alolowed).

You can create a function to check all characters of string are numbers or not, here is C# function

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

You would have to add reference "using System.Linq"

Example

using System;
using System.Linq;
					
public class Program
{
	public static void Main()
	{
		Console.WriteLine(IsNumeric("123"));
		Console.WriteLine(IsNumeric("1a3"));
		Console.WriteLine(IsNumeric("xx223.2"));
		Console.WriteLine(IsNumeric("22.0"));
	}
	
	public static bool IsNumeric(string value)
	{
		return value.All(char.IsNumber);
	}
}

Output:

True
False
False
False

Fiddle https://dotnetfiddle.net/45EqlH

As "22.0" has decimal it will return false.

2
At:- 12/23/2020 2:48:45 PM


profileImage Answered by:- jaya

You can also use Below Code to check if string is number

            Console.WriteLine(Microsoft.VisualBasic.Information.IsNumeric("11")); //true
            Console.WriteLine(Microsoft.VisualBasic.Information.IsNumeric("bbb")); //false
            Console.WriteLine(Microsoft.VisualBasic.Information.IsNumeric("11.334")); //true

You will have to add reference of "Microsoft.VisualBasic" to use above code, which you can do by right-clicking "Reference" -> "Add-Reference"

OR 

You can check each char of a string

    public static bool CheckIfNumeric(string s)
    {
        foreach (char c in s)
        {
            if (!char.IsDigit(c) && c != '.')
            {
                return false;
            }
        }

        return true;
    }

Thanks.

0
At:- 6/21/2022 6:37:41 AM Updated at:- 6/21/2022 6:42:53 AM






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