Winforms – How to show scrollbars on a System.Windows.Forms.TextBox only when the text doesn’t fit

scrollbartextboxwinforms

For a System.Windows.Forms.TextBox with Multiline=True, I'd like to only show the scrollbars when the text doesn't fit.

This is a readonly textbox used only for display. It's a TextBox so that users can copy the text out. Is there anything built-in to support auto show of scrollbars? If not, should I be using a different control? Or do I need to hook TextChanged and manually check for overflow (if so, how to tell if the text fits?)

Not having any luck with various combinations of WordWrap and Scrollbars settings. I'd like to have no scrollbars initially and have each appear dynamically only if the text doesn't fit in the given direction.

@nobugz, thanks, that works when WordWrap is disabled. I'd prefer not to disable wordwrap, but it's the lesser of two evils.

@André Neves, good point, and I would go that way if it was user-editable. I agree that consistency is the cardinal rule for UI intuitiveness.

Best Answer

I came across this question when I wanted to solve the same problem.

The easiest way to do it is to change to System.Windows.Forms.RichTextBox. The ScrollBars property in this case can be left to the default value of RichTextBoxScrollBars.Both, which indicates "Display both a horizontal and a vertical scroll bar when needed." It would be nice if this functionality were provided on TextBox.

Related Solutions

C# – How to automatically scroll to the bottom of a multiline text box

At regular intervals, I am adding new lines of text to it. I would like the textbox to automatically scroll to the bottom-most entry (the newest one) whenever a new line is added.

If you use TextBox.AppendText(string text), it will automatically scroll to the end of the newly appended text. It avoids the flickering scrollbar if you're calling it in a loop.

It also happens to be an order of magnitude faster than concatenating onto the .Text property. Though that might depend on how often you're calling it; I was testing with a tight loop.

This will not scroll if it is called before the textbox is shown, or if the textbox is otherwise not visible (e.g. in a different tab of a TabPanel). See TextBox.AppendText() not autoscrolling. This may or may not be important, depending on if you require autoscroll when the user can't see the textbox.

It seems that the alternative method from the other answers also don't work in this case. One way around it is to perform additional scrolling on the VisibleChanged event:

textBox.VisibleChanged += (sender, e) =>
{
    if (textBox.Visible)
    {
        textBox.SelectionStart = textBox.TextLength;
        textBox.ScrollToCaret();
    }
};

Internally, AppendText does something like this:

textBox.Select(textBox.TextLength + 1, 0);
textBox.SelectedText = textToAppend;

But there should be no reason to do it manually.

^{(If you decompile it yourself, you'll see that it uses some possibly more efficient internal methods, and has what seems to be a minor special case.)}

R – Expandable WinForms TextBox

Same kind of idea as others have posted, put this in your textChanged event:

Dim s As SizeF = TextRenderer.MeasureText(txt.Text, txt.Font, txt.ClientRectangle.Size, TextFormatFlags.WordBreak)
txt.Height = CInt(s.Height)

You will need some kind of minimum height, and possibly to specify some padding, but this does work.

Best Answer

Related Solutions

C# – How to automatically scroll to the bottom of a multiline text box

R – Expandable WinForms TextBox

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