In the Q3 2009 build of RadEditor for ASP.NET AJAX we also introduced two new properties MaxTextLenght and MaxHTMLLength to limit content size. You can use the MaxHtmlLenghtproperty in your scenario.
The MaxTextLengthand MaxHtmlLength properties check the character length only when submitting the content. We decided to implement them in this way because if we check the content length on paste and / or on onkeydown then this will decrease performance and will slow down the typing / editing of large content. This is how these properties are implemented in our competitors' web editors as well.
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