com4:Extension

Article
04/30/2024

Provides functionality to expose COM registrations to clients outside of the app package. The com4 extension is a new version that is a superset of and replacement for the previous COM schema versions. See the Remarks section for more information.

Element hierarchy

<com4:Extension>

Syntax

<com4:Extension
  Category = 'A string that can have one of the following values: "windows.comServer" or "windows.comInterface".'
  Executable = 'An optional string with a value between 1 and 256 characters in length that must end with ".exe" and cannot contain these characters: <, >, :, ", |, ?, or *.'
  EntryPoint = 'An optional string with a value between 1 and 256 characters in length that cannot start or end with a whitespace character.'
  RuntimeType = 'An optional string with a value between 1 and 255 characters in length that cannot start or end with a period or contain these characters: <, >, :, ", /, \, |, ?, or *.'
  StartPage = 'An optional string with a value between 1 and 256 characters in length that cannot contain these characters: <, >, :, ", |, ?, or *.'
  ResourceGroup = 'An optional alphanumeric string with a value between 1 and 255 characters in length. Must begin with a letter.'
  TrustLevel = 'An optional string the can have one of the following values: "appContainer" or "mediumIL".'
  RuntimeBehavior = 'An optional string the can have one of the following values: "windowsApp", "packagedClassicApp", or "win32App".'
  HostId = 'An optional alphanumeric string with a value between 1 and 255 characters in length. Must begin with a letter.'
  Parameters = 'An optional string with a value between 1 and 32767 characters in length with a non-whitespace character at its beginning and end.'
  uap11:Id = 'An optional string with a value between 1 and 255 characters in length with a non-whitespace character at its beginning and end.'
  uap11:Subsystem = 'An optional string that can have one of the following values: "console" or "windows".'
  uap11:SupportsMultipleInstances = 'An optional boolean value.'
  uap11:ResourceGroup = 'An optional alphanumeric string with a value between 1 and 255 characters in length. Must begin with a letter.'
  uap11:CurrentDirectoryPath = 'An optional string that cannot contain these characters: <, >, |, ?, or *. >'
  uap11:Parameters = 'An optional string with a value between 1 and 32767 characters in length with a non-whitespace character at its beginning and end.'
  desktop7:CompatMode = 'An optional string the can have one of the following values: "classic" or "modern".'
  desktop7:Scope = 'An optional string that can have one of the following values: "machine" or "user".' />

  <!-- Child elements -->
  com4:ComServer
  com4:ComInterface

</com4:Extension>

Attributes and elements

Attributes

Attribute	Description	Data type	Required
Category	The type of app extensibility point.	A string that can have one of the following values: windows.comServer or windows.comInterface.	Yes
Executable	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string with a value between 1 and 256 characters in length that must end with `.exe` and cannot contain these characters: `<`, `>`, `:`, `"`, `\|`, `?`, or `*`.	No
EntryPoint	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string with a value between 1 and 256 characters in length that cannot start or end with a whitespace character.	No
RuntimeType	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string with a value between 1 and 255 characters in length that cannot start or end with a period or contain these characters: `<`, `>`, `:`, `"`, `/`, `\`, `\|`, `?`, or `*`.	No
StartPage	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string with a value between 1 and 256 characters in length that cannot contain these characters: `<`, `>`, `:`, `"`, `\|`, `?`, or `*`.	No
ResourceGroup	A tag that you can use to group extension activations together for resource management purposes (for example, CPU and memory). The value you can set ResourceGroup is free-form and flexible. See Application@ResourceGroup.	An optional alphanumeric string with a value between 1 and 255 characters in length. Must begin with a letter.	No
uap10:TrustLevel	Specifies the trust level of the extension. In the current release, this attribute is unsupported for the com4 extension. The value "mediumIL" is always used.	An optional string the can have one of the following values: appContainer or mediumIL.	No
uap10:RuntimeBehavior	Specifies the run time behavior of the extension. In the current release, this attribute is unsupported for the com4 extension. The value "packagedClassicApp" is always used.	An optional string the can have one of the following values: windowsApp, packagedClassicApp, or win32App.	No
uap10:HostId	This value Specifies the ID of the host runtime for the extension.	An optional alphanumeric string with a value between 1 and 255 characters in length. Must begin with a letter.	No
uap10:Parameters	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string with a value between 1 and 32767 characters in length with a non-whitespace character at its beginning and end.	No
uap11:Id	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string with a value between 1 and 255 characters in length with a non-whitespace character at its beginning and end.	No
uap11:Subsystem	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored.	An optional string that can have one of the following values: console or windows.	No
uap11:SupportsMultipleInstances	Specifies whether instances should run in different processes. The default value is false.	An optional boolean value.	No
uap11:ResourceGroup	A tag that you can use to group extension activations together for resource management purposes (for example, CPU and memory). The value you can set ResourceGroup is free-form and flexible. See Application@ResourceGroup.	An optional alphanumeric string with a value between 1 and 255 characters in length. Must begin with a letter.	No
uap11:CurrentDirectoryPath	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored. This attribute supports macros. For more info, see Macros in the package manifest schema.	An optional string that cannot contain these characters: `<`, `>`, `\|`, `?`, or `*`. >	No
uap11:Parameters	This attribute is inherited from the base extension syntax and is not applicable to the com4 extension. Other than syntactic validation, this value is ignored. This attribute supports macros. For more info, see Macros in the package manifest schema.	An optional string with a value between 1 and 32767 characters in length with a non-whitespace character at its beginning and end.	No
desktop7:CompatMode	Specifies whether this extension's information is registered with Windows in classic ways (e.g. unpackaged apps register types with COM via the registry) or in new more scoped ways. The default value is "modern". CompatMode="classic" requires the Microsoft.classicAppCompat_8wekyb3d8bbwe capability.	An optional string the can have one of the following values: classic or modern.	No
desktop7:Scope	Specifies whether the registrations are only visible to other applications running as a user who has this package registered (user), or whether they are visible to all users and services on the machine (machine). The default value is "user". Scope="machine" requires the Microsoft.classicAppCompatElevated_8wekyb3d8bbwe capability.	An optional string that can have one of the following values: machine or user.	No

Child elements

Child element	Description
com4:ComServer	The comServer extension may include class registrations, including activation details for the servers that implement these classes, and ProgId and TreatAsClass registrations, which provide additional identifiers used to reference these classes at runtime.
com4:ComInterface	Declares a package extension point of type windows.comInterface (com4:ComInterface).

Parent elements

Child element	Description
Extensions	Defines one or more extensibility points for the app.

Remarks

The com4 extension is essentially a rewrite of the old windows.comServer/windows.comInterface extension syntax. This extension is a superset of the previous com extension functionality, with identical behavior for the inherited syntax. Manifest validation for the new syntax as used in packaging is better aligned with the semantic requirements of the extension.

In the previous version, each extension was treated as a separate document, allowing non-unique keys and dangling references to be validated.
In the previous version, duplication of attributes subject to unique/key constraints was only caught by manifest validation if the duplicated attributes appear in the same instance of the extension. Packages that duplicated these attributes would fail to deploy, with limited diagnostic information to identify the problem.
In the previous version, a keyref whose referent is in a different instance of the extension would be blocked by manifest validation, which is an artificial restriction relative to what the deployment/runtime behavior support.

Applications targeting Windows 11 that can use the new com4 namespace for all of their windows.comServer/windows.comInterface extensions should use it. Mixing the new namespace with the older namespaces is not recommended, for reasons including:

Deploying the package on versions that support the new namespace will handle extensions from all namespaces, and any unique identifiers duplicated between extensions using different namespace versions will result in a failure. Use of the older namespaces prevents manifest validation from detecting these errors.
Due to limitations of the older namespace schemas, a keyref in the old syntax cannot refer to a key in the new syntax because these are in different instances of the extension.

Use of the following com4 syntax semantics have capability requirements:

CompatMode="classic" requires Microsoft.classicAppCompat_8wekyb3d8bbwe
Scope="machine" requires Microsoft.classicAppCompatElevated_8wekyb3d8bbwe

The following example shows how to register an out-of-process and an in-process server implementation for the same class.

Examples

<com4:Class Id="f4ed7720-9b3a-44a4-xxxx-xxxxxxxxxxxx" DisplayName="CLSID_Foo"/> 
<com:ExeServer Executable="MyServer.exe" DisplayName="My server">  
  <com4:ClassReference Id="f4ed7720-9b3a-44a4-xxxx-xxxxxxxxxxxx"/>  
</com:ExeServer> 
<com4:InProcessServer Path="MyServer.dll">  
  <com4:ClassReference Id="f4ed7720-9b3a-44a4-xxxx-xxxxxxxxxxxx"/>  
</com4:InProcessServer>

New features in the com4 extension

Support for in-process servers (both unmanaged and managed) and custom in-process handlers (that is, not the OLE default handler). This capability is currently functionally limited and restricted by policy:
- This is currently intended for use only by packages with external location; it doesn't work for most normal packages due to ACLs on the install location that prevent the package's dlls from being loaded outside the package. For more information on packages with external location, see Grant package identity by packaging with external location.
It is now possible to associate a TypeLib with a class registration.

Requirements

Item	Value
Namespace	`http://schemas.microsoft.com/appx/manifest/com/windows10/4`
Minimum OS Version	Windows 10 (Build 20348)