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title: "__if_not_exists Statement | Microsoft Docs"
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---
# __if_not_exists Statement
The `__if_not_exists` statement tests whether the specified identifier exists. If the identifier does not exist, the specified statement block is executed.  
  
## Syntax  
  
```  
__if_not_exists ( identifier ) {   
statements  
};  
```  
  
#### Parameters  
  
|Parameter|Description|  
|---------------|-----------------|  
|`identifier`|The identifier whose existence you want to test.|  
|`statements`|One or more statements to execute if `identifier` does not exist.|  
  
## Remarks  
  
> [!CAUTION]
>  To achieve the most reliable results, use the `__if_not_exists` statement under the following constraints.  
  
-   Apply the `__if_not_exists` statement to only simple types, not templates.  
  
-   Apply the `__if_not_exists` statement to identifiers both inside or outside a class. Do not apply the `__if_not_exists` statement to local variables.  
  
-   Use the `__if_not_exists` statement only in the body of a function. Outside of the body of a function, the `__if_not_exists` statement can test only fully defined types.  
  
-   When you test for overloaded functions, you cannot test for a specific form of the overload.  
  
 The complement to the `__if_not_exists` statement is the [__if_exists](../cpp/if-exists-statement.md) statement.  
  
## Example  
 For an example about how to use `__if_not_exists`, see [__if_exists Statement](../cpp/if-exists-statement.md).  
  
## See Also  
 [Selection Statements](../cpp/selection-statements-cpp.md)   
 [Keywords](../cpp/keywords-cpp.md)   
 [__if_exists Statement](../cpp/if-exists-statement.md)