R – causing validation on the textbox

custom-controlsvalidationwinforms

I made a custom text box yesterday with its own validator:

public partial class CustomTextBox : TextBox
{
    ErrorProvider errorProvider;

    public CustomTextBox()
    {            
        InitializeComponent();
        errorProvider = new ErrorProvider();
        errorProvider.DataSource = this;
    }        


    protected override void OnValidating(CancelEventArgs e)
    {
        base.OnValidating(e);
        if (this.Text.Trim() == "")
        {
            errorProvider.SetError(this, "Required field");
            e.Cancel = true;
            return;
        }
        errorProvider.SetError(this, "");
    }


}

So I put this on a form with a cancel button and set causesValidation to false on the cancel button. I also set causesValidation on the form to false. For some reason if I click cancel my customtextbox is still firing the onValidating event. Any ideas what's causing this? I'd like to not have anything validate my text boxes until I click a submit button which will try to validate all controls on the form. This way a user doesn't get forced to enter data into the control before moving on to another. Sound reasonable? This is my first crack at a winforms UI.

Best Answer

Looks like it's a known issue: Visual Studio Feedback.

I set AutoValidate = AutoValidate.Disable; on the form, and it no longer validated. I'm not sure where you'd fit that into your requirement though.

Related Solutions

The maximum length of a valid email address

An email address must not exceed 254 characters.

This was accepted by the IETF following submitted erratum. A full diagnosis of any given address is available online. The original version of RFC 3696 described 320 as the maximum length, but John Klensin subsequently accepted an incorrect value, since a Path is defined as

Path = "<" [ A-d-l ":" ] Mailbox ">"

So the Mailbox element (i.e., the email address) has angle brackets around it to form a Path, which a maximum length of 254 characters to restrict the Path length to 256 characters or fewer.

The maximum length specified in RFC 5321 states:

The maximum total length of a reverse-path or forward-path is 256 characters.

RFC 3696 was corrected here.

People should be aware of the errata against RFC 3696 in particular. Three of the canonical examples are in fact invalid addresses.

I've collated a couple hundred test addresses, which you can find at http://www.dominicsayers.com/isemail

C# – How to make a textbox that only accepts numbers

Two options:

Use a NumericUpDown instead. NumericUpDown does the filtering for you, which is nice. Of course it also gives your users the ability to hit the up and down arrows on the keyboard to increment and decrement the current value.

Handle the appropriate keyboard events to prevent anything but numeric input. I've had success with this two event handlers on a standard TextBox:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) &&
        (e.KeyChar != '.'))
    {
            e.Handled = true;
    }

    // only allow one decimal point
    if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
    {
        e.Handled = true;
    }
}

You can remove the check for '.' (and the subsequent check for more than one '.') if your TextBox shouldn't allow decimal places. You could also add a check for '-' if your TextBox should allow negative values.

If you want to limit the user for number of digit, use: textBox1.MaxLength = 2; // this will allow the user to enter only 2 digits

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