c# check for integers in a textbox

Question

I am trying to check if a textbox contains a number. The problem is that it always returns that it contains a non-numeric character. I've tried several ways, but none of them seems to work.

One of the ways I've tried is:

if( Regex.IsMatch(tb.Text.Trim(), @"^[0-9]+$")) // tb.Text is the textbox 

It does not matter what I enter in the textbox, it always returns that it contains a non-numeric character (I tried entering 1-9, 'a', 'b')

Answer 1

You could just parse the string to a specific number type, ie

double result;
if (!double.TryParse(tb.Text, out result))
{
  //text is not a valid double;
  throw new Exception("not a valid number");
}
//else the value is within the result variable

From your regex it seems that you need only integer values, so you should use int.TryParse or long.TryParse instead.

---

Quick and dirty test program:

void Main()
{
    TestParse("1");
    TestParse("a");
    TestParse("1234");
    TestParse("1a");
}

void TestParse(string text)
{
  int result;
  if (int.TryParse(text, out result))
  {
    Console.WriteLine(text + " is a number");
  }
  else
  {
    Console.WriteLine(text + " is not a number");
  }
}

Results:

1 is a number 
a is not a number  
1234 is a number  
1a is not a number

Answer 2

You could replace your Regex for this:

if(Regex.IsMatch(tb.Text.Trim(), @"[0-9]"))

Or for this:

if(Regex.IsMatch(tb.Text.Trim(), @"\d"))

Answer 3

you can use TryParse:

int value;

bool IsNumber = int.TryParse(tb.Text.Trim(), out value);

if(IsNumber)
{
    //its number
}

Answer 4

private void btnMove_Click(object sender, EventArgs e)
        {
            string check = txtCheck.Text;
            string status = "";
            for (int i = 0; i < check.Length; i++)
            {
                if (IsNumber(check[i]))
                status+="The char at "+i+" is a number\n";
            }
            MessageBox.Show(status);
        }
        private bool IsNumber(char c)
        {
            return Char.IsNumber(c);
        }