Implementing follow-tail on C# multiline textbox

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Hi all,

On a multi-line text box I'm appending text, so its scroll to the bottom on each append. I want to implement follow-tail option (while appending text scroll over the text box) on that multi-line text. Any comments please...

I try to get the number of line up to the bottom edge of the text box and set the scroll to that, but I couldn't do that.

Thanks in advance :)

Posted 19-Nov-13 5:51am

CodingLover

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Sergey Alexandrovich Kryukov 19-Nov-13 11:57am

To start with: if you say "TextBox", the question is: which one? Full type name, please.
Generally, TextBox types are not well suited for appending. Each time you have to read and assign the whole Text. What's the purpose of it? If you use it for a kind of a console, you should better use some other Control or UIElement...
—SA

BillWoodruff 19-Nov-13 12:48pm

Sergey, in WinForms both TextBox and RichTextBox controls provide the AppendText() method (defined in TextBoxBase, from which both inherit), which, I assume, is optimized at a low-level.

That said, in my own practice, I am always trying to find a way to use a StringBuilder which is converted to a String only when necessary.

Sergey Alexandrovich Kryukov 19-Nov-13 13:30pm

Oops! My bad...
Thank you for pointing it out.
—SA

BillWoodruff 19-Nov-13 12:42pm

Please explain exactly what you mean by "follow-tail."

CodingLover 20-Nov-13 8:43am

Its like, in a text box you are keep adding content and it scrolling down to display the latest content. In case I want to see the previous content I have to scroll the vertical scroll bar to the top, but I can't because the content adding scroll down. I just want control that.

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CHill60 · Answer 1 · 2013-11-19T07:10:00

Solution 1

By follow-tail I take it to mean that you want to continuously append text to the end of the textbox and have the textbox automatically scroll so that the new text is visible.

You've already set the text box to multiline, and I advise that you add vertical scrollbar if you haven't already.

The following code will move you to the bottom of the text box each time you add a line

VB

TextBox1.Text += TweetText + System.Environment.NewLine textBox1.SelectionStart = textBox1.Text.Length textBox1.ScrollToCaret()

EDIT - I'll try that again in C# !!!

C#

textBox1.Text += (TweetText) + System.Environment.NewLine;
textBox1.SelectionStart = textBox1.Text.Length;
textBox1.ScrollToCaret();

Where TweetText is a string

Posted 19-Nov-13 7:10am

CHill60

Updated 19-Nov-13 7:14am

v2

Comments

CodingLover 20-Nov-13 8:48am

Thanks for you comment :)

As you said the text box is a multiline text box and I have added vertical scroll bar too. As you know each time I append the text its automatically scroll to the bottom of the text box. I tried the code above, but once I scroll the scroll bar up/down it didn't work. Rather appending at the bottom its added here and there.

CHill60 20-Nov-13 9:00am

Might be worth doing the selectionstart and scrolltocaret before adding the next text rather than the order I put it in above

CodingLover 20-Nov-13 9:13am

I tried that. But then the scroll bar always stuck at top and keep adding the text at the end...

CHill60 20-Nov-13 9:29am

Can you post the line of code you are using to add the new line of text to the text of the textbox?

CodingLover 21-Nov-13 2:49am

Yeah, sure.

if (chkFollowTail.Checked)
{
txtEventResults.AppendText(sbEventRes.ToString());
}
else
{
txtEventResults.SelectionStart = txtEventResults.Text.Length;
txtEventResults.ScrollToCaret();
txtEventResults.Text += sbEventRes.ToString();
}

CHill60 21-Nov-13 8:38am

Well I've tried your code but can't recreate the behaviour! Might be worth raising another question in the forum - make sure you include a reference to this chain so that people don't tag you for reposting, and try to include a summary of where we have got to. I'll have another go at this when I finish work