Context in the Selection Element Identifier
Components should provide context through the selection element identifier (SEID) if they are editors or if they also provide selection information to the Properties window. Most editors provide selection information to the Properties window, as does Solution Explorer. Tool windows, on the other hand, do not provide selection information to the Properties window. Windows that provide selection information to the Properties window can provide context through IVsWindowFrame, and the IDE automatically pushes this context into the SEID.
When the SEID becomes active, it removes any tool window context from the Dynamic Help window. Therefore, if a user has selected the editor and then the task list, which is a tool window, the keyword topics for both the editor and the task list are shown in the Dynamic Help window, with the task list context being of higher priority. If the user then selects the editor, the tool window context disappears. Context of ambient priority is not removed. This approach was devised so that the properties from the editors remain active when a user selects different tool windows.
Solution Explorer also functions like an editor because it pushes its context through the SEID. By providing context through the SEID, Solution Explorer becomes the current editor.