How can I check if a string is a number?

Question

I\'d like to know on C# how to check if a string is a number (and just a number).

Example :

141241   Yes
232a23   No
12412a   No

an

Answer 1

Look up double.TryParse() if you're talking about numbers like 1, -2 and 3.14159. Some others are suggesting int.TryParse(), but that will fail on decimals.

double num;
string candidate = "1";
if (double.TryParse(candidate, out num))
{
    // It's a number!
}

---

EDIT: As Lukas points out below, we should be mindful of the thread culture when parsing numbers with a decimal separator, i.e. do this to be safe:

double.TryParse(candidate, NumberStyles.AllowDecimalPoint, CultureInfo.InvariantCulture, out num)

Answer 2

Yep - you can use the Visual Basic one in C#.It's all .NET; the VB functions IsNumeric, IsDate, etc are actually static methods of the Information class. So here's your code:

using Microsoft.VisualBasic;
...
Information.IsNumeric( object );

Answer 3

If you want to validate if each character is a digit and also return the character that is not a digit as part of the error message validation, then you can loop through each char.

string num = "123x";

foreach (char c in num.ToArray())
{
    if (!Char.IsDigit(c))
    {
        Console.WriteLine("character " + c + " is not a number");
        return;
    }
}

Answer 4

int num;
bool isNumeric = int.TryParse("123", out num);

Answer 5

public static void Main()
        {
            string id = "141241";
            string id1 = "232a23";
            string id2 = "12412a";

            validation( id,  id1,  id2);
        }

       public static void validation(params object[] list)
        {
            string s = "";
            int result;
            string _Msg = "";

            for (int i = 0; i < list.Length; i++)
            {
                s = (list[i].ToString());

               if (string.IsNullOrEmpty(s))
               {
                   _Msg = "Please Enter the value"; 
               }

               if (int.TryParse(s, out result))
               {
                   _Msg = "Enter  " + s.ToString() + ", value is Integer";

               }
               else
               {
                   _Msg = "This is not Integer value ";
               }
            }
        }

Answer 6

I'm not a programmer of particularly high skills, but when I needed to solve this, I chose what is probably a very non-elegant solution, but it suits my needs.

    private bool IsValidNumber(string _checkString, string _checkType)
    {
        float _checkF;
        int _checkI;
        bool _result = false;

        switch (_checkType)
        {
            case "int":
                _result = int.TryParse(_checkString, out _checkI);
                break;
            case "float":
                _result = Single.TryParse(_checkString, out _checkF);
                break;
        }
        return _result;

    }

I simply call this with something like:

if (IsValidNumber("1.2", "float")) etc...

It means that I can get a simple true/false answer back during If... Then comparisons, and that was the important factor for me. If I need to check for other types, then I add a variable, and a case statement as required.