CODEWITHSUNDEEP
c#validation
KMC
KMC

Reputation: 20046

How to validate a field against a Natural Number?

How to validate a TextBox field against a Natural Number? User are restricted to input natural number (e.g. 1,2,3..99999) and if not, a MessageBox is shown.

Currently I'm using the following code (assuming the natural number does not go beyond two digits):

Regex isPositiveNum2 = new Regex("[1-9]");
Regex isPositiveNum = new Regex("[1-9][1-9]");
if (isPositiveNum.IsMatch(textbox1.Text) == true || 
    isPositiveNum2.IsMatch(textbox1.Text) == true)
{
    /* Do something */
}
else
{
    MessageBox.Show("Hey! This is not a Natural Number");
    textbox1.Text = "1";
}

This works alright, but I'm sure it's not the best approach. Hope something can suggest something better.

Upvotes: 2

Views: 2580

Answers (5)

Bolu
Bolu

Reputation: 8786

You can check the char while user entering:

Private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if(!char.IsDigit(e.KeyChar)&&!char.IsControl(e.KeyChar)) //only digit but still allow the user to use control key to Copy&Paste etc. But you need to apply validating with paste text as well
    {
       e.Handled=true;
    }
}

Upvotes: 1

ub1k
ub1k

Reputation: 1674

try this:

int myValue;
if (int.TryParse(mNumTb1.Text, out myValue) && myValue > 0)
{
    //natural
}
else
{
    //not natural
}

Upvotes: 3

Oded
Oded

Reputation: 499002

Use the built in parsing:

int.Parse(textbox1.Text) > 0

This will throw an exception if textbox1.Text can't be parsed, so you may want to use TryParse instead:

int test;
if(int.TryParse(textbox1.Text, out test))
{
  // parse succeeded can check if natural
  if(test > 0)
  {
    // do something
  }
}

Upvotes: 2

agent-j
agent-j

Reputation: 27913

int number;
if (int.TryParse (textbox1.Text, out number) && number >0)
{
    /* Do something */
}
else
{
    MessageBox.Show("Hey! This is not a Natural Number");
    textbox1.Text = "1";
}

Upvotes: 1

Kyle Rosendo
Kyle Rosendo

Reputation: 25277

int i = -1;
int32.TryParse(textbox1.Text, out i);

if (i > 0)
{
    return true;
}
else
{
    return false;
}

Upvotes: 1

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