New to Telerik UI for WinForms? Download free 30-day trial


When developing RadRichTextEditor, we try to optimize the operations being executed as much as possible. However, with the introduction of newer features it cannot be helped that there might be performance diminishments. This article lists some of the known factors that have negative impact on the time that common operations usually take and the overall responsiveness of the UI.

Document Content

The type of the document content also influences the performance. This is only natural, as showing and editing heavily formatted documents take a bigger toll than just previewing plain text.

The performance can be hindered by the following factors:

Large Paragraphs and Words

Large paragraphs can be a hindrance to the overall performance because paragraphs are the main unit of the measure and layout cycle. This means that most of the operations concerning changes in the document (e.g. when you insert, delete or format parts of the document) require an invalidation of the layout of the current paragraph. Therefore, the larger the paragraphs in the document, the worse the performance.

Documents with such big paragraphs are sometimes created when one uses line breaks instead of new paragraphs. In MS Word and in RadRichTextEditor pressing Enter creates a new paragraph, while Shift + Enter inserts a line break. More often than not documents with line-breaks instead of new paragraphs are a result of incorrect code-behind generation of the document, or import of HTML that contains breaks (<br/> tags) instead of paragraph elements (<p></p>) and can be easily avoided.

In addition, words that are longer than one line can also hinder the performance. This is so because processing documents containing such words often results in invalidating large portions of the document. This type of performance issue can be observed when using languages where the words are not separated by intervals, e.g. Japanese, Chinese, etc.


Tables are one of the most complex elements which can be included in a RadDocument. Their behavior in general cases is pretty good, however when a table is extremely large (1000 rows or more) the scrolling/editing experience is diminished.


The term "annotations" stands for anything deriving from AnnotationMarkerBase (see Manipulating Annotations), which includes both “native” and user-defined annotations. This comprises Bookmarks, Hyperlinks, Fields, Comments, Permission and ReadOnly Ranges and Floating Images.

The reason for the impact on the performance is that these elements are kept in special caches in order to enable the specific action that they implement. The more the annotations, the larger the caches, hence the negative effect on the performance.

Headers and Footers, Notes and Comments

It is possible to add headers and footers for each section in the document. The same is also true for Endnotes and Footnotes, as well as Comments. This provides the means for creating even richer documents, but also comes at a price. All this additional content is shown in separate instances of RadRichTextEditor. Furthermore, the contents of the documents of the headers and footers have to be copied across all pages of the section, which may cause performance hindrance with large documents.

In this article