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title: "case (C++) | Microsoft Docs"
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---
# case (C++)
Used with the [switch_type](../windows/switch-type.md) attribute in a **union**.  
  
## Syntax  
  
```  
  
      [ case(  
   value  
) ]  
```  
  
#### Parameters  
 *value*  
 A possible input value for which you want to provide processing. The type of **value** can be one of the following types:  
  
-   `int`  
  
-   `char`  
  
-   `boolean`  
  
-   `enum`  
  
 or an identifier of such a type.  
  
## Remarks  
 The **case** C++ attribute has the same functionality as the **case** MIDL attribute. This attribute is only used with the [switch_type](../windows/switch-type.md) attribute.  
  
## Example  
 The following code shows a use of the **case** attribute:  
  
```  
// cpp_attr_ref_case.cpp  
// compile with: /LD  
#include <unknwn.h>  
[export]  
struct SizedValue2 {  
   [switch_type(char), switch_is(kind)] union {  
      [case(1), string]  
          wchar_t* wval;  
      [default, string]  
          char* val;  
   };  
    char kind;  
};  
[module(name="ATLFIRELib")];  
```  
  
## Requirements  
  
### Attribute Context  
  
|||  
|-|-|  
|**Applies to**|Member of a **class** or `struct`|  
|**Repeatable**|No|  
|**Required attributes**|None|  
|**Invalid attributes**|None|  
  
 For more information about the attribute contexts, see [Attribute Contexts](../windows/attribute-contexts.md).  
  
## See Also  
 [IDL Attributes](../windows/idl-attributes.md)   
 [Typedef, Enum, Union, and Struct Attributes](../windows/typedef-enum-union-and-struct-attributes.md)   
 [Class Attributes](../windows/class-attributes.md)