C# testing to see if a string is an integer?

Question

Hi, I'm just curios as to whether there is something built into either the c# language or the .net framework that tests to see if something is an integer

if (x is an int)
   // Do something

It seems to me that there might be, but I am only a first-year programming student, so I don't know.

Answer 1

Use the int.TryParse method.

string x = "42";
int value;
if(int.TryParse(x, out value))
  // Do something

If it successfully parses it will return true, and the out result will have its value as an integer.

Answer 2

If you just want to check type of passed variable, you could probably use:

    var a = 2;
    if (a is int)
    {
        //is integer
    }
    //or:
    if (a.GetType() == typeof(int))
    {
        //is integer
    }

Answer 3

I think that I remember looking at a performance comparison between int.TryParse and int.Parse Regex and char.IsNumber and char.IsNumber was fastest. At any rate, whatever the performance, here's one more way to do it.

        bool isNumeric = true;
        foreach (char c in "12345")
        {
            if (!Char.IsNumber(c))
            {
                isNumeric = false;
                break;
            }
        }