Clears the file selection in the upload control.
Use the ClearText method to clear the text (file selection) in the upload control. If the file list element is enabled (the UploadAdvancedModeSettings.EnableFileList property is set to
true), the ClearText method removes the selected files from the list.
To remove a particular file from the selection use the ASPxClientUploadControl.RemoveFileFromSelection method.