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title: "threading (C++) | Microsoft Docs"
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---
# threading (C++)
Specifies the threading model for a COM object.  
  
## Syntax  
  
```  
  
      [ threading(  
   model=enumeration  
) ]  
```  
  
#### Parameters  
 ***model*** (optional)  
 One of the following threading models:  
  
-   **apartment** (apartment threading)  
  
-   **neutral** (.NET Framework components with no user interface)  
  
-   **single** (simple threading)  
  
-   **free** (free threading)  
  
-   **both** (apartment and free threading)  
  
 The default value is **apartment**.  
  
## Remarks  
 The **threading** C++ attribute does not appear in the generated .idl file but will be used in the implementation of your COM object.  
  
 In ATL projects, If the [coclass](../windows/coclass.md) attribute is also present, the threading model specified by *model* is passed as the template parameter to the [CComObjectRootEx](../atl/reference/ccomobjectrootex-class.md) class, inserted by the **coclass** attribute.  
  
 The **threading** attribute also guards access to an [event_source](../windows/event-source.md).  
  
## Example  
 See the [licensed](../windows/licensed.md) example for a sample use of **threading**.  
  
## Requirements  
  
### Attribute Context  
  
|||  
|-|-|  
|**Applies to**|**class**, `struct`|  
|**Repeatable**|No|  
|**Required attributes**|**coclass**|  
|**Invalid attributes**|None|  
  
 For more information about the attribute contexts, see [Attribute Contexts](../windows/attribute-contexts.md).  
  
## See Also  
 [COM Attributes](../windows/com-attributes.md)   
 [Typedef, Enum, Union, and Struct Attributes](../windows/typedef-enum-union-and-struct-attributes.md)   
 [Class Attributes](../windows/class-attributes.md)   
 [Multithreading Support for Older Code (Visual C++)](../parallel/multithreading-support-for-older-code-visual-cpp.md)   
 [Neutral Apartments](http://msdn.microsoft.com/library/windows/desktop/ms681813)