Limit textarea with latest data

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This should be easy but I can't find the solution.

I have a readonly multiline-textbox (textarea) that I am using as STDOUT.
Whenever the text data gets too long, I want to delete the oldest lines , thus text won't grow too big.

I add lines with:
textbox01.appendText("hello world\n");

and methods like:

int linecount = textbox01.Lines.count();<br />
string tempstring = textbox01.lines[5];

I want to check if the linecount is greater than 1000, if so, then delete the first (that would be the oldest) 300 lines.
This way the "stdout file" is never more than 1000 lines and it always has the last(recent) lines written.

~~TIA,~~ Thanks in advance,
Jleslie48

Posted 30-Jul-10 4:48am

jleslie48

Updated 30-Jul-10 5:18am

Sandeep Mewara

v3

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3 solutions

Solution 1

Don't use a TextBox.
It is very inefficient for what you want to do - every time to add a line, you generate a whole new string the size of the new textbox content, and copy the one one in!

Use a ListView instead. Set

listView1.View = View.Details;

Then use:

listView1.Items.Add(DateTime.Now.ToString());
while (listView1.Items.Count > 20)
    {
    listView1.Items.RemoveAt(0);
    }

Posted 30-Jul-10 5:10am

OriginalGriff

Solution 2

listview has problems with the user. he can't select all, cut and paste into another program.

remember, I want to use this as stdout, and as such, I want the user to be able to select, cut and paste the output into his/her reports/spreadsheets/documents.

this solution works:

C#

output02.AppendText(textBox1.Text +"\r\n");

//tempstring = output02.Lines[4];
//tempint = output02.Lines.Count();
//tempint = output02.Lines[3].Length;

if (output02.Lines.Count() > 10) { //then
     MessageBox.Show("textbox is over 10 removing first 5 line");
     for (int icount = 0; icount < 5; icount++) {
                      output02.Text = output02.Text.Remove(0,output02.Lines[0].Length+2); //add 2 for the \r\n in the append text.
                      }//for
              }//then


   output02.SelectionStart = output02.Text.Length;
   output02.ScrollToCaret();

but I don't think its optimal.

ps:
"Don't use a TextBox.It is very inefficient for what you want to do - every time to add a line,, you generate a whole new string the size of the new textbox content, and copy the one one in!"

I don't think that is true if you use the .Lines[xxx] method of textboxes.
Listboxes are just a formated textbox, memory management is the same.

textbox.appendtext should be exactly the same as listbox.items.add

Posted 30-Jul-10 5:32am

jleslie48

Updated 31-Jul-10 2:18am

v4

Comments

Toli Cuturicu 31-Jul-10 8:18am

Reason for my vote of 1
fake answer, anyway

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William Winner · Accepted Answer · 2010-07-30T08:40:00

I don't think you understand what the difference really is between a TextBox and a ListBox. Personally, I can see why you wouldn't want a ListBox, but memory management is in no way the same. If you want to see how it's really done, I suggest getting the .NET reflector and looking at it.

A TextBox doesn't store the text as an array of strings representing the lines. When you call .Lines[xxx], the TextBox first builds the array of strings representing each line. Then, it passes the whole array and you select the one you want.

Though AppendText is similar to the ListBox.Items.Add. However, the line deletion will be less efficient.

Anyway, how about this:

C#

output02.Text = output02.Text.Remove(0,output02.GetFirstCharIndexFromLine(5));

Also, just some hints with scrolling and flickering. If you want to pause the redrawing of the textBox so that the user can't see the scroll changing, you can use the code found at: Preventing controls from redrawing[^]

It's in VB, but you should be able to convert it easily. It will make it look better.