CODEWITHSUNDEEP
c#winformstextboxgarbage-collectionoverflow
Novellizator
Novellizator

Reputation: 14893

Why does textbox overflow slow down the program so significantly?

I made an application (something like Google Maps) and I added a textbox field to which debugging data were written (of course I meant to remove it afterwards). The interesting fact is that after it was "full" let's say several kilobytes - the whole program slowed down significantly and needed to be exited because one could not work with it.

Could you please explain?

Upvotes: 1

Views: 532

Answers (2)

Hans Passant
Hans Passant

Reputation: 942090

Well, it is surely more than a couple of kilobytes. But yes, TextBox is pretty unsuitable as a control to display tracing information. Every time you add a new line, it must re-allocate its internal buffer, merging the old text with the new text. It is the exact same kind of problem with .NET's String class. With the StringBuilder class as a workaround, but no equivalent exists for TextBox.

Another option that makes TextBox very slow when you add a lot of lines is the WordWrap property. Setting it to True requires it to do a lot of work to figure out the length of each line every time it paints itself.

So workarounds are to leave WordWrap set to False and to prevent the amount of text from growing boundlessly by throwing half of it away whenever the length reaches a limit. Or by using a different control, TextBox isn't very suitable anyway since it doesn't make sense to edit tracing data. Like ListBox.

Upvotes: 1

Sepster
Sepster

Reputation: 4849

Instead of appending a little data at a time, eg:

debugTextBox.Text += "Some new debug info"

Perhaps this stragegy might be faster:

StringBuilder debugText = new StringBuilder();
...
debugText.Append("Some new debug info");
debugTextBox.Text = debugText.ToString();

(although StringBuilder is probably overkill for this, and may prove slower than just working directly with string concatenations against a string debugText)

Upvotes: 0

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