Input validation in C#.NET

[z3r0aCc3Ss]

Hello, I am now working on C#.NET and VB.NET. Started with C# for now.
I want to validate textboxes for various purposes. Like only integers can be entered or only alphabets (capital/small).
How do I do that?
I wrote following code, but it gave me error:

Code: Select all

        private void button1_Click(object sender, EventArgs e)
        {
            Regex r = new Regex("0-9");

            if (r.IsMatch(textBox1.Text))
            {
                MessageBox.Show("Everything is fine", "Done", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {
                return;
            }
        }

And error took me here:

Code: Select all

this.textBox1.TextChanged += new System.EventHandler(this.textBox1_TextChanged);

Is there any other way by which you can do validation in C#.NET?
How about validation using ASCII codes. I used to do it when I was doing simple VB 6.0.

[z3r0aCc3Ss]

I even tried with ASCII codes. Still the same error.

Code: Select all

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar >= 48 && e.KeyChar <= 57)
            {
                e.Handled = false;
            }
            else
            {
                e.Handled = true;
                MessageBox.Show("Only enter numbers");
            }
        }

[z3r0aCc3Ss]

I did it one way:

Code: Select all

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            try
            {
                System.Int64 i = System.Int64.Parse(textBox1.Text);

                if (i < 1 && i > 9)
                {
                    MessageBox.Show("Please only enter numbers");
                }
            }

            catch (FormatException)
            {
                MessageBox.Show("Please only enter numbers");
            }

But, I don't feel satisfied. First two methods I like the most. Please help. Specially ASCII codes then RegEx.

[ayu]

Did a quick one, is this what you need?

Code: Select all

private void ValidateZipButton_Click(object sender, System.EventArgs e)
{
   String NumRegex = @"^[0-9]+$";

   if(Regex.IsMatch(NumTextBox.Text, NumRegex))
   {
      ResultLabel.Text = "number is valid!";
   }
   else
   {
      ResultLabel.Text = "number is invalid!";
   }
}

[z3r0aCc3Ss]

Yes cats. Its working fine. Thanks,

But I want it to be happened on key press. Instead of showing errors through message box or something, I want to make it in such a way that user will not be able to type anything except numbers. So, we have to use ASCII.

[Gogeta70]

Hmm, i'm no C#.NET coder, but i know windows API and .NET share some similarities, so maybe this will help.

If i had a single-line input control (like a username or password field) and only wanted to accept digits (0-9), i would subclass the control and intercept the WM_CHAR message. Check the wParam value (that's the ascii value of the key that was just pressed) and if it's not numeric, return false.


Basically what i'm saying is that you need to "hijack" the control's character input handler and handle the input yourself.

[Lundis]

Here's one way to do it:

1) use a hooked function such as your textBox1_TextChanged
2) Get the string in the TextBox: String text = textBox1.Text;
3) Remove all invalid characters in the string: String cleansedText = MethodToRemoveInvalidCharacters(text);
4) Set the TextBox string to the cleansed string: textBox1.Text = cleansedText;

[bubzuru]

just check if the char going in on each keypress is a number
if not dont allow it

Code: Select all

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!Char.IsNumber(e.KeyChar)) e.Handled = true;
}

[z3r0aCc3Ss]

bubzuru, its not working dat way...

[bubzuru]

it works fine for me, what errors do you get ?

have you added an on keypress event to your textbox ?

[z3r0aCc3Ss]

I don't get any errors. It doesn't work. Nothing happens...

[z3r0aCc3Ss]

Finally, it worked.
Thank to everyone who helped.

[bubzuru]

for anyone reading this looking for the answer. why didn't it work ? what did you change ?
im guessing you just forgot to add the on keypress event handler