This sample demonstrates how to show a file content in the ASPxSplitter's pane.
Handle the ASPxSplitter's Init event to set the left pane's ContentUrl to "javascript:void(0)". This is a dummy value to force the ASPxSplitter to render an IFrame for its left pane's content. Then handle the ASPxFilemanager's SelectedFileChanged event to pass a file URL to the ASPxSplitter's pane.
This approach will support all files that your browser supports. For example, to view pdf or swf, you need to have corresponding plug-ins installed.