TextBoxMask TextChanging event handler bug

[oenarap]

TextBoxMask leaves an artifact (i.e., old Text value) when a new value is set. (in my case, thru data binding)

since this is just a subtle bug, please allow me to not comply with your required details for this report.

and let me get you directly where i found the offending part of the code:

public partial class TextBoxMask
{
    ...

   private static void Textbox_TextChanging(TextBox textbox, TextBoxTextChangingEventArgs args) 
   {
   ...

    // case adding data at the end of the textbox
    if (oldSelectionStart >= oldText.Length && !isDeleteOrBackspace)
    {
        textbox.Text = oldText;
        if (oldText.Length >= 0)
        {
            textbox.SelectionStart = oldText.Length;
        }
            return;
        }
    ...
    }
}

1. within the if condition, textbox.Text will revert to old value even if you actually intended to assign a completely new/different value to it.

in the subsequent part of the same event handler:

        // Case change due to Text property is assigned a value (Ex Textbox.Text="value")
        if (textbox.SelectionStart == 0 && textbox.FocusState == FocusState.Unfocused)
        {
            var displayText = textbox.GetValue(DefaultDisplayTextProperty) as string ?? string.Empty;
           
            if (string.IsNullOrEmpty(textbox.Text))
            {
                textbox.Text = displayText;
            }
            else
            {
                ...
            }
        }
        ...
        textbox.Text = new string(textArray);
        ...
    }

2. the nested if condition will allow execution of the remaining part of the code which ends up in textbox.Text getting assigned with the old value, even if you actually intend to assign a null/emptly string to it.

here's the quick fix i came up with:

        ...
        // case adding data at the end of the textbox
        if (oldSelectionStart >= oldText.Length && !isDeleteOrBackspace)
        {
            // ignore change(s) if oldtext is a substring of new text value
            if (textbox.Text.Contains(oldText, StringComparison.OrdinalIgnoreCase))
            {
                textbox.Text = oldText;

                if (oldText.Length >= 0)
                {
                    textbox.SelectionStart = oldText.Length;
                }
                
                return;
            }
        }
        ...

        // Case change due to Text property is assigned a value (Ex Textbox.Text="value")
        if (textbox.SelectionStart == 0 && textbox.FocusState == FocusState.Unfocused)
        {
            string displayText = textbox.GetValue(DefaultDisplayTextProperty) as string ?? string.Empty;
            
            if (string.IsNullOrEmpty(textbox.Text))
            {
                textbox.SetValue(OldTextProperty, displayText);
                textbox.SetValue(OldSelectionStartProperty, 0);
                textbox.SetValue(OldSelectionLengthProperty, 0);
                textbox.Text = displayText;
                return;
            }
            else
            {
                ...
            }
        }
        ...

THANKS!

[ghost]

Hello oenarap, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[michael-hawker]

Thanks @oenarap for the report! If you have a fix, do you want to make a PR?

[oenarap]

Thanks @michael-hawker!

PR would be fine with me. For the meantime though, changes i can make could be just a copy of my quick fix included in the bug report. It worked for me, but i'm sure you guys can come up with a better one.

All best!

[oenarap]

hi @michael-hawker. any particular branch that i may be allowed to make a PR?

[Kyaa-dost]

@oenarap you can create a new branch of your own and we can merge that later in the master once the PR is approved 🙂

[Kyaa-dost]

@oenarap not sure if you had a chance but once you have established all the changes in the forked branch then sync your PR with the main branch of WCT and feel free to submit the PR.

Also, feel free to refer to the "Create/Submit the PullRequest" options in our new WIki page for any further guidance you may require.

[Kyaa-dost]

@oenarap please let us know of any updates.