---
description: "Learn more about: case (C++)"
title: "case  (C++ COM Attribute)"
ms.date: "10/02/2018"
f1_keywords: ["vc-attr.case"]
helpviewer_keywords: ["case attribute"]
ms.assetid: 6fb883c3-0526-4932-a901-b4564dcaeb7d
---
# case (C++)

Used with the [switch_type](switch-type.md) attribute in a **`union`**.

## Syntax

```cpp
[ case(value) ]
```

#### Parameters

*value*<br/>
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](switch-type.md) attribute.

## Example

The following code shows a use of the **case** attribute:

```cpp
// 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 | Value |
|-|-|
|**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](cpp-attributes-com-net.md#contexts).

## See also

[IDL Attributes](idl-attributes.md)<br/>
[Typedef, Enum, Union, and Struct Attributes](typedef-enum-union-and-struct-attributes.md)<br/>
[Class Attributes](class-attributes.md)