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

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.

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.

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.