Display empty string on textbox disable

Question

I'm am trying to create a custom TextBox that display an empty string when it is disabled (Enabled = false). When I enable it again, it should display the last value. Also, the Text property should always return the real value, even if it's disabled.

Here is what I have so far, but it's not really working as I want.

Can you help me figure out what is wrong?

public class TestTextBox: System.Windows.Forms.TextBox
{
    private string _text = string.Empty;
    public new string Text
    {
        get
        {
            return _text;
        }
        set
        {
            _text = value;
            base.Text = FormatValue(value);
        }
    }

    protected override void OnEnabledChanged(EventArgs e)
    {
        base.OnEnabledChanged(e);

        base.Text = FormatValue(_text);
    }

    private string FormatValue(string text)
    {
        if(this.Enabled == true)
        {
            return text;
        }
        else
        {
            return string.Empty;
        }
    }
}

What is it doing wrong?

Jeffrey Wieder
– Jeffrey Wieder

2014-09-11 17:22:02 +00:00
Commented Sep 11, 2014 at 17:22 — Jeffrey Wieder
– Jeffrey Wieder, Commented Sep 11, 2014 at 17:22
It won't go back to original text after I enable it.

Pierre-Olivier Goulet
– Pierre-Olivier Goulet

2014-09-11 17:26:22 +00:00
Commented Sep 11, 2014 at 17:26 — Pierre-Olivier Goulet
– Pierre-Olivier Goulet, Commented Sep 11, 2014 at 17:26

ispiro · Accepted Answer · 2014-09-11 17:35:40Z

2

I think the mistake in the code is that typing in it doesn't change its Text property.

If you add a button with:

testTextBox1.Text = "It works";

then enabling and disabling the TestTextBox will toggle between empty and "It works".

EDIT

Add:

protected override void OnTextChanged(EventArgs e)
{
    base.OnTextChanged(e);
    if (Enabled)
        Text = base.Text;
}

edited Sep 11, 2014 at 17:35

answered Sep 11, 2014 at 17:27

ispiro

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3 Comments

TaW Over a year ago

This is a comment, not an answer!

ispiro Over a year ago

@Pierre-OlivierGoulet I tested it. It works. (By the way, +1 on the question. non-trivial mistake there.)

Pierre-Olivier Goulet Over a year ago

Yeah, it works as long as I don't type in the textbox... How can I make it work also when typing?

TaW · Accepted Answer · 2014-09-11 17:27:28Z

2

How about something like this:

protected override void OnEnabledChanged(EventArgs e)
{
    base.OnEnabledChanged(e);

    this.ForeColor = this.Enabled ? SystemColors.ControlText : this.BackColor;
}

If you want to support other ForeColors you can store the current one in a Property and use it instead of SystemColors.ControlText.

answered Sep 11, 2014 at 17:27

TaW

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4 Comments

Bedford Over a year ago

This is by far the simplest solution. You can also use Color.Transparent instead of this.BackColor

TaW Over a year ago

Yes, I have come to stay away from Transparency, but it ought to work here ;-)

Pierre-Olivier Goulet Over a year ago

While this wokrs, I'll keep it as a last resort because it is not 'politicaly correct'...

TaW Over a year ago

Well I thought so myself and in fact a spy tool would be able to read the text. But if that's the concern I guess that solution will be the least of your concerns. Being disabled the text can't be selected either, which would make it visible, so i guess it is safe enough.

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