Only accept number in textbox

[jasonli]

I just figured it out. Now post the source code here and hope anybody help me test it. Want it be perfect.

Thanks a lot.

int iCaret = 0;
private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
    TextBox txt = (TextBox)sender;

    switch (e.KeyCode)
    {
        case Keys.Left:
            iCaret = ((iCaret - 1) < 0) ? 0 : (iCaret - 1);
            break;
        case Keys.Right:
            iCaret = ((iCaret + 1) > txt.Text.Length) ? txt.Text.Length : (iCaret + 1);
            break;
        case Keys.Home:
            iCaret = 0;
            break;
        case Keys.End:
            iCaret = txt.Text.Length;
            break;
        case Keys.Back:
            iCaret = ((iCaret - 1) < 0) ? 0 : (iCaret - 1);
            break;
        default:
            break;
    }
}
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    TextBox txt = (TextBox)sender;

    if (e.KeyChar != 8 && iCaret == 0 && txt.Text.Contains("-"))
    {
        e.Handled = true;
        return;
    }
    if (char.IsDigit(e.KeyChar) || e.KeyChar == 8)
        e.Handled = false;
    else
    {
        if (e.KeyChar == '-')
        {
            if (!txt.Text.Contains("-"))
            {
                txt.Text = "-" + txt.Text;
                iCaret++;
                txt.Select(iCaret, 0);
            }
            e.Handled = true;
        }
        else if (e.KeyChar == '.')
        {
            e.Handled = txt.Text.Contains(".");
        }
        else
            e.Handled = true;
    }

    if (!e.Handled && e.KeyChar != 8)
        iCaret++;
}

[BigEd781]

I would recommend using a regular expression. Much shorter and cleaner.

http://www.codeguru.com/forum/showth...66#post1792166

[jasonli]

I would recommend using a regular expression. Much shorter and cleaner.

http://www.codeguru.com/forum/showth...66#post1792166

I tried that way, but I failed to type in minus number.

Thanks.

[BigEd781]

I tried that way, but I failed to type in minus number.

Thanks.

That just means that your RegEx is incorrect. That switch statement is hard to understand, but a simple RegEx is a one liner and most will know immediately what you are trying to do.

[Arjay]

Any reason you can't just set the style on the textbox to only accept numbers?

[jasonli]

That just means that your RegEx is incorrect. That switch statement is hard to understand, but a simple RegEx is a one liner and most will know immediately what you are trying to do.

I searched a lot for regular expression and finally got "^[+-]?\d+\.?\d*$", which can validate mostly, not completely. I put validation in KeyPress event because I don't wanna show invalid character in textbox.

any idea?

Any reason you can't just set the style on the textbox to only accept numbers?

I did not find any property about this for textbox in Windows form. Thank you anyway.

[Shuja Ali]

I have always found it easier to use a numericUpDown control. After all this can also act as a text box control. Just set the some properties properly and there you go. Without writing any code, you have a numeric textbox.

Also take a look at this article on MSDN
http://msdn.microsoft.com/en-us/library/ms229644.aspx

[jasonli]

I have always found it easier to use a numericUpDown control. After all this can also act as a text box control. Just set the some properties properly and there you go. Without writing any code, you have a numeric textbox.

Also take a look at this article on MSDN
http://msdn.microsoft.com/en-us/library/ms229644.aspx

NumericTextBox is a very nice class. I did not try this yet. I'm just wondering what will happen if user inputs "87432.-90". I am gonna try this.

Thanks.

[JonnyPoet]

Why not simple use a filter so only numbers can reach the textbox.
You can do it in the keydown event delegate of your texboxes like

public void TextBox1_ KeyDown(KeyEventArgs e) {
MathSignsOnly(e); 
}
private void MathSignsOnly(KeyEventArgs e) {
    if (!((e.KeyCode >= Keys.D0 && e.KeyCode <= Keys.D9 && !e.Shift) || (e.KeyCode >= Keys.NumPad0 && e.KeyCode <= Keys.NumPad9) ||
        e.KeyCode == Keys.Oemcomma || e.KeyCode == Keys.OemPeriod || e.KeyCode == Keys.Back || e.KeyCode == Keys.Decimal || e.KeyCode == Keys.Delete ||
        e.KeyCode == Keys.Enter || e.KeyCode == Keys.Escape || e.KeyCode == Keys.NumLock || e.KeyCode == Keys.Right ||
        e.KeyCode == Keys.Left || e.KeyCode == Keys.Home || e.KeyCode == Keys.End)) {
        e.SuppressKeyPress = true;
    }
}

I'm using such filters together with a decorator. This way I can have different filters for different textboxes. They all get exactly that filter they need.
The above filter allowes unsigned decimal values only but no alphabet letters. This way you can supress everything you want if you want a minus sign simple add it here. If you want keyUp KeyDown, Left, right simple add them to be allowed

[jasonli]

Why not simple use a filter so only numbers can reach the textbox.
You can do it in the keydown event delegate of your texboxes like

public void TextBox1_ KeyDown(KeyEventArgs e) {
MathSignsOnly(e); 
}
private void MathSignsOnly(KeyEventArgs e) {
    if (!((e.KeyCode >= Keys.D0 && e.KeyCode <= Keys.D9 && !e.Shift) || (e.KeyCode >= Keys.NumPad0 && e.KeyCode <= Keys.NumPad9) ||
        e.KeyCode == Keys.Oemcomma || e.KeyCode == Keys.OemPeriod || e.KeyCode == Keys.Back || e.KeyCode == Keys.Decimal || e.KeyCode == Keys.Delete ||
        e.KeyCode == Keys.Enter || e.KeyCode == Keys.Escape || e.KeyCode == Keys.NumLock || e.KeyCode == Keys.Right ||
        e.KeyCode == Keys.Left || e.KeyCode == Keys.Home || e.KeyCode == Keys.End)) {
        e.SuppressKeyPress = true;
    }
}

I'm using such filters together with a decorator. This way I can have different filters for different textboxes. They all get exactly that filter they need.
The above filter allowes unsigned decimal values only but no alphabet letters. This way you can supress everything you want if you want a minus sign simple add it here. If you want keyUp KeyDown, Left, right simple add them to be allowed

Almost perfect one! It can't prevent user typing "459.54-98".
I added lots of source code to prevent this.

Thank you.

[JonnyPoet]

Almost perfect one! It can't prevent user typing "459.54-98".
I added lots of source code to prevent this.

Thank you.

This needs to be handled in the decorator Formatting method which simple checks the mathematical value of the textbox and if a minus is contained in the input its always formatted to the beginning of the value so it never could be set to the end of a value.
Simple but effective.
Are you already done with your code or have you still troubles ?
If so I would extract the code of my dll for this one method and zip an example for you. If you are already done, I wouldn't do as its per sure an hour of work to copy it to an demo-project and looking if all neded methods are included. Its not much code, but the work is to only copy that part which is used for one textbox and uses the IDecimalUnsigned Interface which I have designed for that. Because having different formatts needed in any program I have designed a family of such decorators so I only need to use the correct one for a given purpose and this way all my textboxes are protected against wrong input.
The advantage of this is that you are pressing a key and it instantly reacts while validation normally works after you have finished input.
So when I type 123- then it does 123 and when I type the minus it instantly writes -123 Whats about 123.01.01 is your code also disallowing wrong input like this ?

[cjard]

Really, it's like Shuja said; use a numericupdown control. If you need to screw in a screw, use a screwdriver, not a chisel, hammer, knife etc..

[cjard]

I'm just wondering what will happen if user inputs "87432.-90".

In an NUD? nothing. It wont work

[JonnyPoet]

In an NUD? nothing. It wont work

Simple try it. Set maimum and minimum Range as you need it, set DecimalPlaces to your needs e.g '2' and Increment to 0.01

Then test it if this does what you want. If you do a wrong input like "12.98-98" the input will vanish as soon as you click to the next field because its validated obviously when leaving it. But Clicking to a toolstrip Button does nothing, there is still the wrong value there and numericUpDown1. Value is Zero

I dont know if that fits your needs for me this wasn't acceptable as in programs working with finances a wrong input needs an errorindication so it couldn't be overlooked that there was a typo which killed my input. ( I dont think the user intentionally puts in wrong data but when I look to our 10 finger typing secretary girls they type and type and sometimes their fingers slip a bit and the Enter key was missed and the input of two fields is now in one. In this case they get a red asterix to the wrong input fields.

But just about the theme of whats the best way of error prevention and errorhandling and the best way of input validation you can fill books IMHO

[jasonli]

I really appreciate you guy's inputs. Even though I don't get the better solution, I have learnt a lot from you guys. Thank you very much.

Like cjard said, I used a knife to screw in a screw. Anyway, my code is working. I am gonna use it until better one comes out.

JonnyPoet, thank you for your offer. For now I don't have trouble to implement the function, so you don't need to waste time copying codes on this.

Finally, I just wanna say, "no coding, no function." You can't have everything done by only setting some properties.

Thank you guys again! Happy coding!