Extern element
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
The Extern element references any external header (.h) files to merge with the .vsct file at compile time. The files to be merged must be on the Include path given to the VSCT compiler or referenced by an Include element. The files may be other .vsct files or C++ header files.
Definitions in header files must be of the form "#define [Symbol] [Value]" The value may be another symbol if it is previously defined. Definitions may be used in conditional statements of command items. Any symbol not actually used will be discarded.
CommandTable Element Extern Element
Syntax
<Extern href="stdidcmd.h" />
Attributes and elements
The following sections describe attributes, child elements, and parent elements.
Attributes
| Attribute | Description |
|---|---|
| href | Required. The path to the header file: href="stdidcmd.h" |
| Condition | Optional. See Conditional attributes. |
| language | Optional. The default language of all <Strings> elements in the command table: language="en-us" |
Child elements
| Element | Description |
|---|---|
| None. | None. |
Parent elements
| Element | Description |
|---|---|
| CommandTable element | Defines all of the elements that represent commands — that is, menu items, menus, toolbars, and combo boxes — that a VSPackage provides to the IDE. |
Example
<?xml version="1.0" encoding="utf-8"?>
<CommandTable xmlns="http://schemas.microsoft.com/VisualStudio/2005-10-
18/CommandTable" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<Extern href="C:\VSCore\vscommon\inc\vsshlids.h"/>
...
<Commands package="guidMyPackage">
</CommandTable>