Mike,
I have no problem adding one million lines to my TextBox. I also tried 100 million lines but then I got a system out of memory exception LOL
Are you talking about million of lines of 100 of million of lines?

>How do you populate the TextBox? Using the Text property? The Text property is a String type and the limit for a String type is around 2 billion characters so that might be the limit.
>How do you append a new log line to your TextBox? Are you using the StringBuilder or just a String?
>I would just keep 500 (or 1000) lines in the TextBox and then write the lod log lines to a text file.
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>Einar
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>>I am using it to log a process that is going on. It seems that after so many lines, it just stops outputting. I don't have a count though...