How to validate user input for whether it's an

Question

It tells me that it can't convert int to bool. Tried TryParse but for some reason the argument list is invalid.

Code:

private void SetNumber(string n)
{
    // if user input is a number then
    if (int.Parse(n)) 
    {
        // if user input is negative
        if (h < 0)
        {
            // assign absolute version of user input
            number = Math.Abs(n); 
        }
        else 
        {
            // else assign user input
            number = n;
        }
    }
    else
    {
        number = 0; // if user input is not an int then set number to 0  
    }
}

Answer 1

There are a lot of problems with this code:

• Using VB-style line comments (') instead of C# slashes
• Parse for integer returns an int and not a bool
• You should use TryParse with an out value
• h does not seem to be valid at all. Is it a type for n?
• There are variables that do not seem to be defined in function scope (number) are they defined at class scope?

But try this:

private void SetNumber(string n)
{
    int myInt;
    if (int.TryParse(n, out myInt)) //if user input is a number then
    {
        if (myInt < 0) //if user input is negative
            number = Math.Abs(n); //assign absolute version of user input
        else //else assign user input
            number = n;
    }
    else number = 0; //if user input is not an int then set number to 0
}

Answer 2

Well for one thing the inner if statement has an 'h' instead of an 'n' if(h < 0). But TryParse should work there assuming that 'number' is a class variable.

 private void SetNumber(string n)
    {
        int temp;
        bool success = Int32.TryParse(n, out temp);

        // If conversion successful
        if (success)
        {
            // If user input is negative
            if (temp < 0)
                number = Math.Abs(temp); // Assign absolute version of user input
            else // Assign user input
                number = temp;

        }
        else
        {
            number = 0;
        }

    }

Answer 3

You were probably very close using TryParse, but I'm guessing you forgot the out keyword on the parameter:

int value;
if (int.TryParse(n, out value))
{

}

Answer 4

You can try with some simple regular expression :

  bool IsNumber(string text)
    {
      Regex regex = new Regex(@"^[-+]?[0-9]*\.?[0-9]+$");
      return regex.IsMatch(text);
    }