keypress in C#

[hoobas20]

here's my code:

 private void keypress_charOnly(object sender, KeyPressEventArgs e)
        {
            

            int ascii = Convert.ToInt16(e.KeyChar);
            if ((ascii >= 97 && ascii <= 122) || (ascii == 8) || (ascii >= 65 && ascii <= 90))

                {
                    e.Handled = false;
                }
            else
                {
                    e.Handled = true;

                }
               
         }

my question is, how can i prevent user to input integer values.
copy and paste (using mouse) can bypass the keypress event..
thanks.

[jmcilhinney]

char keyChar = e.KeyChar;
 
e.Handled == char.IsDigit(keyChar);

If the character is a digit then e.Handled is true and the character is rejected. Just note that that won't prevent digits being pasted in via the clipboard.

[hoobas20]

What event will I going to paste that code?

[hoobas20]

I Got it!

     private void textBox1_TextChanged(object sender, EventArgs e)
        {
            bool isNum;
            int num;
            isNum = Int32.TryParse(textBox1.Text, out num);

            if (!isNum)
            {
                MessageBox.Show("not numeric");
                textBox1.Text = "0";
                textBox1.SelectionStart = 0;
                textBox1.SelectionLength = textBox1.Text.Length;

            }
               
               
        }

Thanks for replying!

[jmcilhinney]

The "proper" way to do this would be to handle the KeyPress event to prevent invalid characters being typed in and then override the WndProc method to intercept WM_PASTE (I think) messages to prevent invalid data being pasted in. What you've done will do a job but it's a bit of a hack, plus it could get rather annoying to the user if they type 10 valid characters and then accidentally type an invalid one and you wipe out the entire text. It also means that the user can't clear the TextBox and start typing because your code will stick a zero in there.

[hoobas20]

Sir, I want to adapt your code but. I don't know how to use that. I get some error.

 private void keypress_charOnly(object sender, KeyPressEventArgs e)
        {
              
                char keyChar = e.KeyChar;
                e.Handled == char.IsDigit(keyChar); 
        }

Is this the proper way in doing that? Sorry again.. I am new in C#..

[jmcilhinney]

First up, in your original post you said:

my question is, how can i prevent user to input integer values.

That says that you don't want the user to enter any numbers. I'm guessing now that that's just the language barrier and what you actually want is for the user to enter nothing but numbers. Is that correct? If so then the code would be:

char keyChar = e.KeyChar;
 
e.Handled == !char.IsControl(keyChar) && !char.IsDigit(keyChar);

in the KeyPress event handler.

[hoobas20]

I still get an error.

[high6]

shouldn't that be 1 = not 2?

[jmcilhinney]

shouldn't that be 1 = not 2?

Absolutely. Sorry about that.

e.Handled = !char.IsControl(keyChar) && !char.IsDigit(keyChar);

Not quite sure why I did that. Stupidity maybe?

[hoobas20]

It still bypass the copy paste. what should i do?

[Quasar6]

Here's another way to do this, which is more processor intensive, but is much less annoying.

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            foreach (char i in textBox1.Text)
            {
                if (!char.IsDigit(i))
                {
                    textBox1.Text = textBox1.Text.Replace(i.ToString(), "");
                }
            }
        }

The only problem with it is that it returns the text curser to the front of the text box every time you input an invalid character. Remove the "!" if you want only text, leave it there if you want only numbers.

Cheers,
Qu.

[acpt]

Thanks !

However, this does not allow entering "."
I need to allow the user to enter a value like "3.25"

How do I do this ?

[jmcilhinney]

Thanks !

However, this does not allow entering "."
I need to allow the user to enter a value like "3.25"

How do I do this ?

Post #10 shows how to combine multiple conditions. You simply need to add another condition that checks whether the KeyChar is a decimal point.

[gep13]

Hey,

If you are wanting a control that only accepts numbers, why not simply use a NumericUpDown control?

Otherwise, have a look at this thread here:

http://www.vbforums.com/showthread.php?t=583495

Gary